Eye glint imaging in see-through computer display systems

ABSTRACT

Disclosure herein concerns a method that includes illuminating a user&#39;s eye with an illumination source in a head-worn display, capturing an image of the user&#39;s eye with an eye camera in the head-worn display, wherein the image includes an eye glint produced by light from the illumination source that is reflected from a surface of the user&#39;s eye, determining a size of an eye glint in the captured image, and identifying a change in focus distance for the user&#39;s eye in correspondence with a change in the size of the eye glint.

I. CLAIM OF PRIORITY

This application is a continuation of U.S. Non-Provisional applicationSer. No. 16/776,174, filed on Jan. 29, 2020.

U.S. Non-Provisional application Ser. No. 16/776,174, filed on Jan. 29,2020 is a continuation of U.S. Non-Provisional application Ser. No.15/815,119, filed on Nov. 16, 2017, U.S. Pat. No. 10,579,140, issued onMar. 3, 2020.

U.S. Non-Provisional application Ser. No. 15/815,119, filed on Nov. 16,2017 is a continuation of U.S. Non-Provisional application Ser. No.14/884,567, filed on Oct. 15, 2015, U.S. Pat. No. 9,836,122, issued onDec. 5, 2017.

U.S. Non-Provisional application Ser. No. 14/884,567, filed on Oct. 15,2015, is a continuation-in-part of U.S. Non-Provisional application Ser.No. 14/218,606, filed on Mar. 18, 2014, U.S. Pat. No. 10,191,279, issuedon Jan. 29, 2019.

U.S. Non-Provisional application Ser. No. 14/218,606, filed on Mar. 18,2014, is a continuation-in-part of U.S. Non-Provisional application Ser.No. 14/216,175, filed on Mar. 17, 2014, U.S. Pat. No. 9,298,007, issuedon Mar. 29, 2016.

U.S. Non-Provisional application Ser. No. 14/216,175 is acontinuation-in-part of the following U.S. patent applications: U.S.Non-Provisional application Ser. No. 14/160,377, entitled OpticalConfigurations for Head Worn Computing, filed on Jan. 21, 2014, nowabandoned; U.S. Non-Provisional application Ser. No. 14/172,901,entitled Optical Configurations for Head Worn Computing, filed on Feb.4, 2014, now abandoned, which is a continuation-in-part of U.S.Non-Provisional application Ser. No. 14/163,646, filed on Jan. 24, 2014,U.S. Pat. No. 9,400,390, issued on Jul. 26, 2016; and U.S.Non-Provisional application Ser. No. 14/181,459, entitled Suppression ofStray Light in Head Worn Computing, filed on Feb. 14, 2014, U.S. Pat.No. 9,715,112, issued on Jul. 25, 2017, which is a continuation-in-partof U.S. Non-Provisional application Ser. No. 14/178,047, filed on Feb.11, 2014, U.S. Pat. No. 9,229,233, issued on Jan. 5, 2016.

U.S. Non-Provisional application Ser. No. 14/884,567, filed Oct. 15,2015, U.S. Pat. No. 9,836,122, issued on Dec. 5, 2017, is acontinuation-in-part of U.S. Non-Provisional application Ser. No.14/254,253, entitled Eye Imaging in Head Worn Computing, filed on Apr.16, 2014, U.S. Pat. No. 9,952,664, issued Apr. 24, 2018.

U.S. Non-Provisional application Ser. No. 14/254,253 claims the benefitof priority to and is a continuation-in-part of U.S. Non-Provisionalapplication Ser. No. 14/325,991, entitled Optical Configurations forHead-Worn See-Through Displays, filed on Jul. 8, 2014, U.S. Pat. No.9,366,867, issued on Jun. 14, 2016.

All of the above applications are incorporated herein by reference intheir entirety.

II. BACKGROUND A. Field of the Invention

This invention relates to see-through computer display systems.

B. Description of Related Art

Head mounted displays (HMDs) and particularly HMDs that provide asee-through view of the environment are valuable instruments. Thepresentation of content in the see-through display can be a complicatedoperation when attempting to ensure that the user experience isoptimized. Improved systems and methods for presenting content in thesee-through display are required to improve the user experience.

III. SUMMARY

Aspects of the present invention relate to methods and systems for thesee-through computer display systems with conversion ability fromaugmented reality (i.e. high see-through transmission through thedisplay) to virtual reality (i.e. low or no see-through transmissionthrough the display).

In an aspect, a head-worn display may include a display panel sized andpositioned to produce a field of view to present digital content to aneye of a user, and a processor adapted to present the digital content tothe display panel such that the digital content is only presented in aportion of the field of view, the portion being in the middle of thefield of view such that horizontally opposing edges of the field of vieware blank areas. The processor may be further adapted to shift thedigital content into one of the blank areas to adjust the convergencedistance of the digital content and thereby change the perceiveddistance from the user to the digital content. The digital content mayinclude augmented reality objects. The perceived distance may be withinarm's reach by the user. The convergence distance may be adjusted incorrespondence to the type of digital content being displayed or a usecase associated with augmented reality objects. The convergence may bemeasured by an eye imaging system of the head-worn display. The eyeimaging system images a front perspective of the user's eye.

In an aspect, a head-worn display may include a display panel sized andpositioned to produce a field of view to present digital content to aneye of a user and a processor adapted to present the digital content tothe display panel such that the digital content is only presented in aportion of the field of view, the portion being in the middle of thefield of view such that horizontally opposing edges of the field of vieware blank areas. The processor may be further adapted to shift thedigital content into one of the blank areas to adjust the position ofthe digital content based on a focus distance of the digital content.

In an aspect, a head-worn display may include a display panel sized andpositioned to produce a field of view to present digital content to aneye of a user and a processor adapted to present the digital content tothe display panel such that the digital content is only presented in aportion of the field of view, the portion being in the middle of thefield of view such that horizontally opposing edges of the field of vieware blank areas. The processor may be further adapted to shift thedigital content into one of the blank areas to adjust the position ofthe digital content based on an indication that the user is lookingtowards an edge of the digital content. The indication that the user islooking towards an edge of the digital content may be based on an eyeimage captured by a camera in the head-worn display. The indication thatthe user is looking towards an edge of the digital content may be basedon an indication that the user turned the user's head followed quicklyby the user turning the user's eyes.

In an aspect, a head-worn display may include a display panel sized andpositioned to produce a field of view to present digital content to aneye of a user and a processor adapted to present the digital content tothe display panel such that the digital content is only presented in aportion of the field of view, the portion being in the middle of thefield of view such that horizontally opposing edges of the field of vieware blank areas, wherein each blank area comprises approximately 10% orgreater of the field of view lateral area. The processor may be furtheradapted to shift the digital content into one of the blank areas toadjust the position of the digital content. A total amount of blank areain the field of view, including a combined left and right portion of thefield of view, remains constant while the left and right portions arechanged to position the digital content within the field of view. Thedigital content may be positioned to adjust a convergence distanceassociated with the digital content. The digital content may bepositioned to adjust an interpupillary distance associated with thedigital content.

These and other systems, methods, objects, features, and advantages ofthe present invention will be apparent to those skilled in the art fromthe following detailed description of the preferred embodiment and thedrawings. All documents mentioned herein are hereby incorporated intheir entirety by reference.

IV. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are described with reference to the following Figures. Thesame numbers may be used throughout to reference like features andcomponents that are shown in the Figures:

FIG. 1 illustrates a head worn computing system in accordance with theprinciples of the present invention.

FIG. 2 illustrates a head worn computing system with optical system inaccordance with the principles of the present invention.

FIG. 3a illustrates a large prior art optical arrangement.

FIG. 3b illustrates an upper optical module in accordance with theprinciples of the present invention.

FIG. 4 illustrates an upper optical module in accordance with theprinciples of the present invention.

FIG. 4a illustrates an upper optical module in accordance with theprinciples of the present invention.

FIG. 4b illustrates an upper optical module in accordance with theprinciples of the present invention.

FIG. 5 illustrates an upper optical module in accordance with theprinciples of the present invention.

FIG. 5a illustrates an upper optical module in accordance with theprinciples of the present invention.

FIG. 5b illustrates an upper optical module and dark light trapaccording to the principles of the present invention.

FIG. 5c illustrates an upper optical module and dark light trapaccording to the principles of the present invention.

FIG. 5d illustrates an upper optical module and dark light trapaccording to the principles of the present invention.

FIG. 5e illustrates an upper optical module and dark light trapaccording to the principles of the present invention.

FIG. 6 illustrates upper and lower optical modules in accordance withthe principles of the present invention.

FIG. 7 illustrates angles of combiner elements in accordance with theprinciples of the present invention.

FIG. 8 illustrates upper and lower optical modules in accordance withthe principles of the present invention.

FIG. 8a illustrates upper and lower optical modules in accordance withthe principles of the present invention.

FIG. 8b illustrates upper and lower optical modules in accordance withthe principles of the present invention.

FIG. 8c illustrates upper and lower optical modules in accordance withthe principles of the present invention.

FIG. 9 illustrates an eye imaging system in accordance with theprinciples of the present invention.

FIG. 10 illustrates a light source in accordance with the principles ofthe present invention.

FIG. 10a illustrates a back lighting system in accordance with theprinciples of the present invention.

FIG. 10b illustrates a back lighting system in accordance with theprinciples of the present invention.

FIGS. 11a to 11d illustrate light source and filters in accordance withthe principles of the present invention.

FIGS. 12a to 12c illustrate light source and quantum dot systems inaccordance with the principles of the present invention.

FIGS. 13a to 13c illustrate peripheral lighting systems in accordancewith the principles of the present invention.

FIGS. 14a to 14h illustrate a light suppression systems in accordancewith the principles of the present invention.

FIG. 15 illustrates an external user interface in accordance with theprinciples of the present invention.

FIGS. 16a to 16c illustrate distance control systems in accordance withthe principles of the present invention.

FIGS. 17a to 17c illustrate force interpretation systems in accordancewith the principles of the present invention.

FIGS. 18a to 18c illustrate user interface mode selection systems inaccordance with the principles of the present invention.

FIG. 19 illustrates interaction systems in accordance with theprinciples of the present invention.

FIG. 20 illustrates external user interfaces in accordance with theprinciples of the present invention.

FIG. 21 illustrates mD trace representations presented in accordancewith the principles of the present invention.

FIG. 22 illustrates mD trace representations presented in accordancewith the principles of the present invention.

FIG. 23 illustrates an mD scanned environment in accordance with theprinciples of the present invention.

FIG. 23a illustrates mD trace representations presented in accordancewith the principles of the present invention.

FIG. 24 illustrates a stray light suppression technology in accordancewith the principles of the present invention.

FIG. 25 illustrates a stray light suppression technology in accordancewith the principles of the present invention.

FIG. 26 illustrates a stray light suppression technology in accordancewith the principles of the present invention.

FIG. 27 illustrates a stray light suppression technology in accordancewith the principles of the present invention.

FIGS. 28a to 28c illustrate DLP mirror angles.

FIGS. 29 to 33 illustrate eye imaging systems according to theprinciples of the present invention.

FIGS. 34 and 34 a illustrate structured eye lighting systems accordingto the principles of the present invention.

FIG. 35 illustrates eye glint in the prediction of eye directionanalysis in accordance with the principles of the present invention.

FIG. 36a illustrates eye characteristics that may be used in personalidentification through analysis of a system according to the principlesof the present invention.

FIG. 36b illustrates a digital content presentation reflection off ofthe wearer's eye that may be analyzed in accordance with the principlesof the present invention.

FIG. 37 illustrates eye imaging along various virtual target lines andvarious focal planes in accordance with the principles of the presentinvention.

FIG. 38 illustrates content control with respect to eye movement basedon eye imaging in accordance with the principles of the presentinvention.

FIG. 39 illustrates eye imaging and eye convergence in accordance withthe principles of the present invention.

FIG. 40 illustrates content position dependent on sensor feedback inaccordance with the principles of the present invention.

FIG. 41 illustrates content position dependent on sensor feedback inaccordance with the principles of the present invention.

FIG. 42 illustrates content position dependent on sensor feedback inaccordance with the principles of the present invention.

FIG. 43 illustrates content position dependent on sensor feedback inaccordance with the principles of the present invention.

FIG. 44 illustrates content position dependent on sensor feedback inaccordance with the principles of the present invention.

FIG. 45 illustrates various headings over time in an example.

FIG. 46 illustrates content position dependent on sensor feedback inaccordance with the principles of the present invention.

FIG. 47 illustrates content position dependent on sensor feedback inaccordance with the principles of the present invention.

FIG. 48 illustrates content position dependent on sensor feedback inaccordance with the principles of the present invention.

FIG. 49 illustrates content position dependent on sensor feedback inaccordance with the principles of the present invention.

FIG. 50 illustrates light impinging an eye in accordance with theprinciples of the present invention.

FIG. 51 illustrates a view of an eye in accordance with the principlesof the present invention.

FIGS. 52a and 52b illustrate views of an eye with a structured lightpattern in accordance with the principles of the present invention.

FIG. 53 illustrates an optics module in accordance with the principlesof the present invention.

FIG. 54 illustrates an optics module in accordance with the principlesof the present invention.

FIG. 55 shows a series of example spectrum for a variety of controlledsubstances as measured using a form of infrared spectroscopy.

FIG. 56 shows an infrared absorbance spectrum for glucose.

FIGS. 56a, 56b, 56c, and 56d depict examples of eye glints.

FIG. 56e depicts a chart of the measured anterior and posteriorspherical radii of the eye of a person.

FIG. 57 illustrates a scene where a person is walking with a HWC mountedon his head.

FIG. 58 illustrates a system for receiving, developing and usingmovement heading, sight heading, eye heading and/or persistenceinformation from HWC(s).

FIG. 59 illustrates a presentation technology in accordance with theprinciples of the present invention.

FIG. 60 illustrates a presentation technology in accordance with theprinciples of the present invention.

FIG. 61 illustrates a presentation technology in accordance with theprinciples of the present invention.

FIG. 62 illustrates a presentation technology in accordance with theprinciples of the present invention.

FIG. 63 illustrates a presentation technology in accordance with theprinciples of the present invention.

FIG. 64 illustrates a presentation technology in accordance with theprinciples of the present invention.

FIG. 65 illustrates a presentation technology in accordance with theprinciples of the present invention.

FIG. 66 illustrates a presentation technology in accordance with theprinciples of the present invention.

FIG. 67 illustrates an optical configuration in accordance with theprinciples of the present invention.

FIG. 68 illustrates an optical configuration in accordance with theprinciples of the present invention.

FIG. 69 illustrates an optical configuration in accordance with theprinciples of the present invention.

FIG. 70 illustrates an optical configuration in accordance with theprinciples of the present invention.

FIG. 71 illustrates an optical configuration in accordance with theprinciples of the present invention.

FIG. 72 illustrates an optical element in accordance with the principlesof the present invention.

FIG. 73 illustrates an optical element in accordance with the principlesof the present invention.

FIG. 74 illustrates an optical element in accordance with the principlesof the present invention.

FIG. 75 illustrates an optical element in accordance with the principlesof the present invention.

FIG. 76 illustrates an optical element in a see-through computer displayin accordance with the principles of the present invention.

FIG. 77 illustrates an optical element in accordance with the principlesof the present invention.

FIG. 78 illustrates an optical element in accordance with the principlesof the present invention.

FIG. 79a illustrates a schematic of an upper optic in accordance withthe principles of the present invention.

FIG. 79 illustrates a schematic of an upper optic in accordance with theprinciples of the present invention.

FIG. 80 illustrates a stray light control technology in accordance withthe principles of the present invention.

FIGS. 81a and 81b illustrate a display with a gap and maskedtechnologies in accordance with the principles of the present invention.

FIG. 82 illustrates an upper module with a trim polarizer in accordancewith the principles of the present invention.

FIG. 83 illustrates an optical system with a laminated multiplepolarizer film in accordance with the principles of the presentinvention.

FIGS. 84a and 84b illustrate partially reflective layers in accordancewith the principles of the present invention.

FIG. 84c illustrates a laminated multiple polarizer with a complex curvein accordance with the principles of the present invention.

FIG. 84d illustrates a laminated multiple polarizer with a curve inaccordance with the principles of the present invention.

FIG. 85 illustrates an optical system adapted for a head-mounted displayin accordance with the principles of the present invention.

FIG. 86 illustrates an optical system adapted for a head-mounted displayin accordance with the principles of the present invention.

FIG. 87 illustrates an optical system adapted for a head-mounted displayin accordance with the principles of the present invention.

FIG. 88 illustrates an optical system adapted for a head-mounted displayin accordance with the principles of the present invention.

FIG. 89 illustrates an optical system adapted for a head-mounted displayin accordance with the principles of the present invention.

FIG. 90 illustrates an optical system adapted for a head-mounted displayin accordance with the principles of the present invention.

FIG. 91 illustrates an optical system in accordance with the principlesof the present invention.

FIG. 92 illustrates an optical system in accordance with the principlesof the present invention.

FIG. 93 illustrates an optical system in accordance with the principlesof the present invention.

FIG. 94 illustrates an optical system in accordance with the principlesof the present invention.

FIG. 95 illustrates an optical system in accordance with the principlesof the present invention.

FIG. 96 illustrates an optical system in accordance with the principlesof the present invention.

FIG. 97 illustrates an optical system in accordance with the principlesof the present invention.

FIG. 98 illustrates an optical system in accordance with the principlesof the present invention.

FIG. 99 illustrates an optical system in accordance with the principlesof the present invention.

FIG. 100 illustrates an optical system in accordance with the principlesof the present invention.

FIG. 101 illustrates an optical system in accordance with the principlesof the present invention.

FIG. 102 illustrates an optical system in accordance with the principlesof the present invention.

FIGS. 103, 103 a and 103 b illustrate optical systems in accordance withthe principles of the present invention.

FIG. 104 illustrates an optical system in accordance with the principlesof the present invention.

FIG. 105 illustrates a blocking optic in accordance with the principlesof the present invention.

FIGS. 106a, 106b, and 106c illustrate a blocking optic system inaccordance with the principles of the present invention.

FIG. 107 illustrates a full color image in accordance with theprinciples of the present invention.

FIGS. 108A and 108B illustrate color breakup management in accordancewith the principles of the present invention.

FIG. 109 illustrates timing sequences in accordance with the principlesof the present invention.

FIG. 110 illustrates timing sequences in accordance with the principlesof the present invention.

FIGS. 111a and 111b illustrate sequentially displayed images inaccordance with the principles of the present invention.

FIG. 112 illustrates a see-through display with rotated components inaccordance with the principles of the present invention.

FIG. 113 illustrates an optics module with twisted reflective surfacesin accordance with the principles of the present invention.

FIG. 114 illustrates PCB and see-through optics module positions withina glasses form factor in accordance with the principles of the presentinvention.

FIG. 115 illustrates PCB and see-through optics module positions withina glasses form factor in accordance with the principles of the presentinvention.

FIG. 116 illustrates PCB and see-through optics module positions withina glasses form factor in accordance with the principles of the presentinvention.

FIG. 117 illustrates a user interface in accordance with the principlesof the present invention.

FIG. 118 illustrates a user interface in accordance with the principlesof the present invention.

FIG. 119 illustrates a lens arrangement in accordance with theprinciples of the present invention.

FIGS. 120 and 121 illustrate eye imaging systems in accordance with theprinciples of the present invention.

FIG. 122 illustrates an identification process in accordance with theprinciples of the present invention.

FIGS. 123 and 124 illustrate combiner assemblies in accordance with theprinciples of the present invention.

FIG. 125 shows a chart of the sensitivity of the human eye versusbrightness.

FIG. 126 is a chart that shows the brightness (L*) perceived by thehuman eye relative to a measured brightness (luminance) of a scene.

FIG. 127 is illustration of a see-through view of the surroundingenvironment with an outline showing the display field of view beingsmaller than the see-through field of view as is typical.

FIG. 128 is an illustration of a captured image of the surroundingenvironment which can be a substantially larger field of view than thedisplayed image so that a cropped version of the captured image of theenvironment can be used for the alignment process.

FIGS. 129a and 129b illustrate first and second target images withinvisible markers.

FIGS. 130 and 131 illustrate targets overlaid onto a see-through view,wherein the target is moved using eye tracking control, in accordancewith the principles of the present invention.

FIG. 132 shows an illustration of multiply folded optics for a head worndisplay that includes a solid prism in accordance with the principles ofthe present invention.

FIGS. 133a, 133b and 133c show illustrations of steps associated withbonding the reflective plate to the solid prism in accordance with theprinciples of the present invention.

FIG. 134 shows an illustration of multiply folded optics for areflective image source with a backlight assembly positioned behind thereflective plate in accordance with the principles of the presentinvention.

FIG. 135 shows an illustration of a prism film bonded to a reflectiveplate in accordance with the principles of the present invention.

FIG. 135a shows an illustration of multiply folded optics in which twocones of illumination light provided by the prism film are shown inaccordance with the principles of the present invention.

FIGS. 136, 137 and 138 show illustrations of different embodiments ofadditional optical elements included in the solid prism for imaging theeye of the user in accordance with the principles of the presentinvention.

FIG. 139 shows an illustration of an eye imaging system for multiplyfolded optics in which the image source is a self-luminous display inaccordance with the principles of the present invention.

FIGS. 140a and 140b are illustrations of an eye imaging system inaccordance with the principles of the present invention.

FIGS. 141a and 141b are illustrations of folded optics that include awaveguide with an angled partially reflective surface and a poweredreflective surface in accordance with the principles of the presentinvention.

FIGS. 142a and 142b are illustrations of folded optics for a head-worndisplay that include waveguides with at least one holographic opticalelement and image source in accordance with the principles of thepresent invention.

FIG. 143 is an illustration of folded optics for a head-worn display inwhich the illumination light is injected into the waveguide andredirected by the holographic optical element so that the user's eye isilluminated in accordance with the principles of the present invention.

FIG. 144 shows an illustration of folded optics for a head-worn displaywhere a series of angled partial mirrors are included in the waveguidein accordance with the principles of the present invention.

FIG. 145 shows an illustration of a beam splitter based optical modulefor a head-worn display in accordance with the principles of the presentinvention.

FIG. 146 shows an illustration of an optical module for a head-worndisplay in accordance with the principles of the present invention.

FIG. 146a shows an illustration of a side view of an optics module thatincludes a corrective lens element.

FIG. 147 shows an illustration of left and right optics modules that areconnected together in a chassis in accordance with the principles of thepresent invention.

FIG. 148 shows the left and right images provided at the nominalvergence distance within the left and right display fields of view inaccordance with the principles of the present invention.

FIG. 149 shows how the left and right images are shifted laterallytowards each other within the left and right display fields of view inaccordance with the principles of the present invention.

FIGS. 150a and 150b show a mechanism for moving the image source inaccordance with the principles of the present invention.

FIGS. 151a and 151b show illustrations of an upper wedge and lower wedgefrom the position of the image source in accordance with the principlesof the present invention.

FIG. 152 shows an illustration of spring clips applying a force to animage source in accordance with the principles of the present invention.

FIGS. 153a, 153b and 154 shows illustrations of example display opticsthat include eye imaging in accordance with the principles of thepresent invention.

FIGS. 155a, 155b, 156a, 156b, 157a, 157b, 158a, 158b, 159a and 159b showillustrations of focus adjustment modules in accordance with theprinciples of the present invention.

FIG. 160 shows an illustration of an example of multiply folded opticsas viewed from the eye position in accordance with the principles of thepresent invention.

FIGS. 161 and 162 illustrate optical systems in accordance with theprinciples of the present invention.

FIG. 163A illustrates an abrupt change in appearance of content in thefield of view of a see-through display.

FIG. 163B illustrates a managed appearance system where the content isreduced in appearance as it enters a transitional zone near the edge ofthe field of view.

FIG. 164 illustrates a hybrid field of view that includes a centeredfield of view and an extended field of view that is positioned at ornear or overlapping with an edge of the centered field of view.

FIG. 165 illustrates a hybrid display system where the main, centered,field of view is generated with optics in an upper module and theextended field of view is generated with a display system mounted abovethe combiner.

FIGS. 166A-166D illustrate examples of extended display, or extendedimage content optic, configurations.

FIG. 167 illustrates another optical system that uses a hybrid opticalsystem that includes a main display optical system and an extended fieldof view optical system.

FIGS. 168A-168E illustrate various embodiments where a see-throughdisplay panel is positioned directly in front of the user's eye in thehead-worn computer to provide the extended and/or overlapping field ofview in a hybrid display system.

FIG. 169 shows a cross sectional illustration of an example opticsassembly for a head worn display in accordance with the principles ofthe present invention.

FIG. 170 shows an illustration of the light trap operating to reducestray light in accordance with the principles of the present invention.

FIG. 171 shows an illustration of a simple optical system that providesa 60 degree display field of view in accordance with the principles ofthe present invention.

FIG. 172 shows a chart of the acuity of a typical human eye relative tothe angular position in the field of view.

FIG. 173 shows a chart of the typical acuity of the human eye vs theeccentricity in a simplified form that highlights the dropoff in acuitywith eccentricity along with the difference between achromatic acuityand chromatic acuity.

FIG. 174A and FIG. 174B show typical angular eye movements and headmovements given in radians vs time.

FIG. 175 is a chart that shows the effective relative achromatic acuity,compared to the acuity of the fovea, provided by a typical human eyewithin the eye's field of view when the movement of the eye is included.

FIG. 176 is a chart that shows the minimum design MTF vs angular fieldposition needed to provide a uniformly sharp looking image in a widefield of view displayed image.

FIG. 177 is a chart that shows the relative MTF needed to be provided bythe display optics for a wide field of view display to provide asharpness that matches the acuity of the human eye in the peripheralzone of the display field of view.

FIG. 178 shows a modeled MTF curve associated with the optical system ofFIG. 171 wherein MTF curves for a variety of different angular positionswithin the display field of view are shown.

FIG. 179 is an illustration of a resolution chart wherein the sharpnessof the image has been reduced by blurring the peripheral portion of theimage to simulate an image from optics that provide a central sharp zoneof +/−15 degrees with a peripheral zone that is less sharp.

FIGS. 180 and 181 are illustrations that show how the image is shiftedwithin the display field of view as the user moves their head inaccordance with the principles of the present invention.

FIG. 182 illustrates the blank portion of the display field of viewwhere the image has been shifted away from is displayed as a dark regionto enable the user to see-through to the surrounding environment in theblank portion in accordance with the principles of the presentinvention.

FIG. 183 shows an illustration of a wide display field of view, whereina user can choose to display a smaller field of view for a given imageor application (e.g. a game) to improve the personal viewing experiencein accordance with the principles of the present invention.

FIGS. 184 and 185 should physical arrangements of optical systems inaccordance with the principles of the present invention.

FIG. 186 shows a 30:9 format field of view and a 22:9 format field ofview, wherein the two fields of view have the same vertical field ofview and different horizontal field of view in accordance with theprinciples of the present invention.

FIG. 187 depicts the user's eyes looking through display fields of view.

FIG. 188 depicts a lateral image shift within the display fields ofview.

FIG. 189 depicts an illustration of the left and right displayed imagesas they would be presented within the display fields of view.

FIG. 190 depicts an illustration of the left and right displayed imagesas they would be presented within the display fields of view.

FIG. 191 depicts shows an illustration of the user's eyes lookingthrough display fields of view.

FIG. 192 depicts an illustration of the left and right displayed imagesas they would be presented within the display fields of view.

While the invention has been described in connection with certainpreferred embodiments, other embodiments would be understood by one ofordinary skill in the art and are encompassed herein.

V. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Aspects of the present invention relate to head-worn computing (“HWC”)systems. HWC involves, in some instances, a system that mimics theappearance of head-worn glasses or sunglasses. The glasses may be afully developed computing platform, such as including computer displayspresented in each of the lenses of the glasses to the eyes of the user.In embodiments, the lenses and displays may be configured to allow aperson wearing the glasses to see the environment through the lenseswhile also seeing, simultaneously, digital imagery, which forms anoverlaid image that is perceived by the person as a digitally augmentedimage of the environment, or augmented reality (“AR”).

HWC involves more than just placing a computing system on a person'shead. The system may need to be designed as a lightweight, compact andfully functional computer display, such as wherein the computer displayincludes a high resolution digital display that provides a high level ofemersion comprised of the displayed digital content and the see-throughview of the environmental surroundings. User interfaces and controlsystems suited to the HWC device may be required that are unlike thoseused for a more conventional computer such as a laptop. For the HWC andassociated systems to be most effective, the glasses may be equippedwith sensors to determine environmental conditions, geographic location,relative positioning to other points of interest, objects identified byimaging and movement by the user or other users in a connected group,and the like. The HWC may then change the mode of operation to match theconditions, location, positioning, movements, and the like, in a methodgenerally referred to as a contextually aware HWC. The glasses also mayneed to be connected, wirelessly or otherwise, to other systems eitherlocally or through a network. Controlling the glasses may be achievedthrough the use of an external device, automatically throughcontextually gathered information, through user gestures captured by theglasses sensors, and the like. Each technique may be further refineddepending on the software application being used in the glasses. Theglasses may further be used to control or coordinate with externaldevices that are associated with the glasses.

Referring to FIG. 1, an overview of the HWC system 100 is presented. Asshown, the HWC system 100 comprises a HWC 102, which in this instance isconfigured as glasses to be worn on the head with sensors such that theHWC 102 is aware of the objects and conditions in the environment 114.In this instance, the HWC 102 also receives and interprets controlinputs such as gestures and movements 116. The HWC 102 may communicatewith external user interfaces 104. The external user interfaces 104 mayprovide a physical user interface to take control instructions from auser of the HWC 102 and the external user interfaces 104 and the HWC 102may communicate bi-directionally to affect the user's command andprovide feedback to the external device 108. The HWC 102 may alsocommunicate bi-directionally with externally controlled or coordinatedlocal devices 108. For example, an external user interface 104 may beused in connection with the HWC 102 to control an externally controlledor coordinated local device 108. The externally controlled orcoordinated local device 108 may provide feedback to the HWC 102 and acustomized GUI may be presented in the HWC 102 based on the type ofdevice or specifically identified device 108. The HWC 102 may alsointeract with remote devices and information sources 112 through anetwork connection 110. Again, the external user interface 104 may beused in connection with the HWC 102 to control or otherwise interactwith any of the remote devices 108 and information sources 112 in asimilar way as when the external user interfaces 104 are used to controlor otherwise interact with the externally controlled or coordinatedlocal devices 108. Similarly, HWC 102 may interpret gestures 116 (e.g.captured from forward, downward, upward, rearward facing sensors such ascamera(s), range finders, IR sensors, etc.) or environmental conditionssensed in the environment 114 to control either local or remote devices108 or 112.

We will now describe each of the main elements depicted on FIG. 1 inmore detail; however, these descriptions are intended to provide generalguidance and should not be construed as limiting. Additional descriptionof each element may also be further described herein.

The HWC 102 is a computing platform intended to be worn on a person'shead. The HWC 102 may take many different forms to fit many differentfunctional requirements. In some situations, the HWC 102 will bedesigned in the form of conventional glasses. The glasses may or may nothave active computer graphics displays. In situations where the HWC 102has integrated computer displays the displays may be configured assee-through displays such that the digital imagery can be overlaid withrespect to the user's view of the environment 114. There are a number ofsee-through optical designs that may be used, including ones that have areflective display (e.g. LCoS, DLP), emissive displays (e.g. OLED, LED),hologram, TIR waveguides, and the like. In embodiments, lighting systemsused in connection with the display optics may be solid state lightingsystems, such as LED, OLED, quantum dot, quantum dot LED, etc. Inaddition, the optical configuration may be monocular or binocular. Itmay also include vision corrective optical components. In embodiments,the optics may be packaged as contact lenses. In other embodiments, theHWC 102 may be in the form of a helmet with a see-through shield,sunglasses, safety glasses, goggles, a mask, fire helmet withsee-through shield, police helmet with see through shield, militaryhelmet with see-through shield, utility form customized to a certainwork task (e.g. inventory control, logistics, repair, maintenance,etc.), and the like.

The HWC 102 may also have a number of integrated computing facilities,such as an integrated processor, integrated power management,communication structures (e.g. cell net, WiFi, Bluetooth, local areaconnections, mesh connections, remote connections (e.g. client server,etc.)), and the like. The HWC 102 may also have a number of positionalawareness sensors, such as GPS, electronic compass, altimeter, tiltsensor, IMU, and the like. It may also have other sensors such as acamera, rangefinder, hyper-spectral camera, Geiger counter, microphone,spectral illumination detector, temperature sensor, chemical sensor,biologic sensor, moisture sensor, ultrasonic sensor, and the like.

The HWC 102 may also have integrated control technologies. Theintegrated control technologies may be contextual based control, passivecontrol, active control, user control, and the like. For example, theHWC 102 may have an integrated sensor (e.g. camera) that captures userhand or body gestures 116 such that the integrated processing system caninterpret the gestures and generate control commands for the HWC 102. Inanother example, the HWC 102 may have sensors that detect movement (e.g.a nod, head shake, and the like) including accelerometers, gyros andother inertial measurements, where the integrated processor mayinterpret the movement and generate a control command in response. TheHWC 102 may also automatically control itself based on measured orperceived environmental conditions. For example, if it is bright in theenvironment the HWC 102 may increase the brightness or contrast of thedisplayed image. In embodiments, the integrated control technologies maybe mounted on the HWC 102 such that a user can interact with itdirectly. For example, the HWC 102 may have a button(s), touchcapacitive interface, and the like.

As described herein, the HWC 102 may be in communication with externaluser interfaces 104. The external user interfaces may come in manydifferent forms. For example, a cell phone screen may be adapted to takeuser input for control of an aspect of the HWC 102. The external userinterface may be a dedicated UI, such as a keyboard, touch surface,button(s), joy stick, and the like. In embodiments, the externalcontroller may be integrated into another device such as a ring, watch,bike, car, and the like. In each case, the external user interface 104may include sensors (e.g. IMU, accelerometers, compass, altimeter, andthe like) to provide additional input for controlling the HWD 104.

As described herein, the HWC 102 may control or coordinate with otherlocal devices 108. The external devices 108 may be an audio device,visual device, vehicle, cell phone, computer, and the like. Forinstance, the local external device 108 may be another HWC 102, whereinformation may then be exchanged between the separate HWCs 108.

Similar to the way the HWC 102 may control or coordinate with localdevices 106, the HWC 102 may control or coordinate with remote devices112, such as the HWC 102 communicating with the remote devices 112through a network 110. Again, the form of the remote device 112 may havemany forms. Included in these forms is another HWC 102. For example,each HWC 102 may communicate its GPS position such that all the HWCs 102know where all of HWC 102 are located.

FIG. 2 illustrates a HWC 102 with an optical system that includes anupper optical module 202 and a lower optical module 204. While the upperand lower optical modules 202 and 204 will generally be described asseparate modules, it should be understood that this is illustrative onlyand the present invention includes other physical configurations, suchas that when the two modules are combined into a single module or wherethe elements making up the two modules are configured into more than twomodules. In embodiments, the upper module 202 includes a computercontrolled display (e.g. LCoS, DLP, OLED, etc.) and image light deliveryoptics. In embodiments, the lower module includes eye delivery opticsthat are configured to receive the upper module's image light anddeliver the image light to the eye of a wearer of the HWC. In FIG. 2, itshould be noted that while the upper and lower optical modules 202 and204 are illustrated in one side of the HWC such that image light can bedelivered to one eye of the wearer, that it is envisioned by the presentinvention that embodiments will contain two image light deliverysystems, one for each eye.

FIG. 3b illustrates all upper optical module 202 in accordance with theprinciples of the present invention. In this embodiment, the upperoptical module 202 includes a DLP (also known as DMD or digitalmicromirror device) computer operated display 304 which includes pixelscomprised of rotatable mirrors (such as, for example, the DLP3000available from Texas Instruments), polarized light source 302, ¼ waveretarder film 308, reflective polarizer 310 and a field lens 312. Thepolarized light source 302 provides substantially uniform polarizedlight that is generally directed towards the reflective polarizer 310.The reflective polarizer reflects light of one polarization state (e.g.S polarized light) and transmits light of the other polarization state(e.g. P polarized light). The polarized light source 302 and thereflective polarizer 310 are oriented so that the polarized light fromthe polarized light source 302 is reflected generally towards the DLP304. The light then passes through the ¼ wave film 308 once beforeilluminating the pixels of the DLP 304 and then again after beingreflected by the pixels of the DLP 304. In passing through the ¼ wavefilm 308 twice, the light is converted from one polarization state tothe other polarization state (e.g. the light is converted from S to Ppolarized light). The light then passes through the reflective polarizer310. In the event that the DLP pixel(s) are in the “on” state (i.e. themirrors are positioned to reflect light towards the field lens 312, the“on” pixels reflect the light generally along the optical axis and intothe field lens 312. This light that is reflected by “on” pixels andwhich is directed generally along the optical axis of the field lens 312will be referred to as image light 316. The image light 316 then passesthrough the field lens to be used by a lower optical module 204.

The light that is provided by the polarized light source 302, which issubsequently reflected by the reflective polarizer 310 before itreflects from the DLP 304, will generally be referred to as illuminationlight. The light that is reflected by the “off” pixels of the DLP 304 isreflected at a different angle than the light reflected by the “on”pixels, so that the light from the “off” pixels is generally directedaway from the optical axis of the field lens 312 and toward the side ofthe upper optical module 202 as shown in FIG. 3. The light that isreflected by the “off” pixels of the DLP 304 will be referred to as darkstate light 314.

The DLP 304 operates as a computer controlled display and is generallythought of as a MEMS device. The DLP pixels are comprised of smallmirrors that can be directed. The mirrors generally flip from one angleto another angle. The two angles are generally referred to as states.When light is used to illuminate the DLP the mirrors will reflect thelight in a direction depending on the state. In embodiments herein, wegenerally refer to the two states as “on” and “off,” which is intendedto depict the condition of a display pixel. “On” pixels will be seen bya viewer of the display as emitting light because the light is directedalong the optical axis and into the field lens and the associatedremainder of the display system. “Off” pixels will be seen by a viewerof the display as not emitting light because the light from these pixelsis directed to the side of the optical housing and into a light trap orlight dump where the light is absorbed. The pattern of “on” and “off”pixels produces image light that is perceived by a viewer of the displayas a computer generated image. Full color images can be presented to auser by sequentially providing illumination light with complimentarycolors such as red, green and blue. Where the sequence is presented in arecurring cycle that is faster than the user can perceive as separateimages and as a result the user perceives a full color image comprisedof the sum of the sequential images. Bright pixels in the image areprovided by pixels that remain in the “on” state for the entire time ofthe cycle, while dimmer pixels in the image are provided by pixels thatswitch between the “on” state and “off” state within the time of thecycle, or frame time when in a video sequence of images.

FIG. 3a shows an illustration of a system for a DLP 304 in which theunpolarized light source 350 is pointed directly at the DLP 304. In thiscase, the angle required for the illumination light is such that thefield lens 352 must be positioned substantially distant from the DLP 304to avoid the illumination light from being clipped by the field lens352. The large distance between the field lens 352 and the DLP 304 alongwith the straight path of the dark state light 354, means that the lighttrap for the dark state light 354 is also located at a substantialdistance from the DLP. For these reasons, this configuration is largerin size compared to the upper optics module 202 of the preferredembodiments.

The configuration illustrated in FIG. 3b can be lightweight and compactsuch that it fits into a small portion of a HWC. For example, the uppermodules 202 illustrated herein can be physically adapted to mount in anupper frame of a HWC such that the image light can be directed into alower optical module 204 for presentation of digital content to awearer's eye. The package of components that combine to generate theimage light (i.e. the polarized light source 302, DLP 304, reflectivepolarizer 310 and ¼ wave film 308) is very light and is compact. Theheight of the system, excluding the field lens, may be less than 8 mm.The width (i.e. from front to back) may be less than 8 mm. The weightmay be less than 2 grams. The compactness of this upper optical module202 allows for a compact mechanical design of the HWC and the lightweight nature of these embodiments help make the HWC lightweight toprovide for a HWC that is comfortable for a wearer of the HWC.

The configuration illustrated in FIG. 3b can produce sharp contrast,high brightness and deep blacks, especially when compared to LCD or LCoSdisplays used in HWC. The “on” and “off” states of the DLP provide for astrong differentiator in the light reflection path representing an “on”pixel and an “off” pixel. As will be discussed in more detail below, thedark state light from the “off” pixel reflections can be managed toreduce stray light in the display system to produce images with highcontrast.

FIG. 4 illustrates another embodiment of an upper optical module 202 inaccordance with the principles of the present invention. This embodimentincludes a light source 404, but in this case, the light source canprovide unpolarized illumination light. The illumination light from thelight source 404 is directed into a TIR wedge 418 such that theillumination light is incident on an internal surface of the TIR wedge418 (shown as the angled lower surface of the TIR wedge 418 in FIG. 4)at an angle that is beyond the critical angle as defined by Eqn 1.

Critical angle=arc−sin(1/n)  Eqn 1

Where the critical angle is the angle beyond which the illuminationlight is reflected from the internal surface when the internal surfacecomprises an interface from a solid with a higher refractive index (n)to air with a refractive index of 1 (e.g. for an interface of acrylic,with a refractive index of n=1.5, to air, the critical angle is 41.8degrees; for an interface of polycarbonate, with a refractive index ofn=1.59, to air the critical angle is 38.9 degrees). Consequently, theTIR wedge 418 is associated with a thin air gap 408 along the internalsurface to create an interface between a solid with a higher refractiveindex and air. By choosing the angle of the light source 404 relative tothe DLP 402 in correspondence to the angle of the internal surface ofthe TIR wedge 418, illumination light is turned toward the DLP 402 at anangle suitable for providing image light 414 as reflected from “on”pixels. Wherein, the illumination light is provided to the DLP 402 atapproximately twice the angle of the pixel mirrors in the DLP 402 thatare in the “on” state, such that after reflecting from the pixelmirrors, the image light 414 is directed generally along the opticalaxis of the field lens. Depending on the state of the DLP pixels, theillumination light from “on” pixels may be reflected as image light 414which is directed towards a field lens and a lower optical module 204,while illumination light reflected from “off” pixels (generally referredto herein as “dark” state light, “off” pixel light or “off” state light)410 is directed in a separate direction, which may be trapped and notused for the image that is ultimately presented to the wearer's eye.

The light trap for the dark state light 410 may be located along theoptical axis defined by the direction of the dark state light 410 and inthe side of the housing, with the function of absorbing the dark statelight. To this end, the light trap may be comprised of an area outsideof the cone of image light 414 from the “on” pixels. The light trap istypically made up of materials that absorb light including coatings ofblack paints or other light absorbing materials to prevent lightscattering from the dark state light degrading the image perceived bythe user. In addition, the light trap may be recessed into the wall ofthe housing or include masks or guards to block scattered light andprevent the light trap from being viewed adjacent to the displayedimage.

The embodiment of FIG. 4 also includes a corrective wedge 420 to correctthe effect of refraction of the image light 414 as it exits the TIRwedge 418. By including the corrective wedge 420 and providing a thinair gap 408 (e.g. 25 micron), the image light from the “on” pixels canbe maintained generally in a direction along the optical axis of thefield lens (i.e. the same direction as that defined by the image light414) so it passes into the field lens and the lower optical module 204.As shown in FIG. 4, the image light 414 from the “on” pixels exits thecorrective wedge 420 generally perpendicular to the surface of thecorrective wedge 420 while the dark state light exits at an obliqueangle. As a result, the direction of the image light 414 from the “on”pixels is largely unaffected by refraction as it exits from the surfaceof the corrective wedge 420. In contrast, the dark state light 410 issubstantially changed in direction by refraction when the dark statelight 410 exits the corrective wedge 420.

The embodiment illustrated in FIG. 4 has the similar advantages of thosediscussed in connection with the embodiment of FIG. 3b . The dimensionsand weight of the upper module 202 depicted in FIG. 4 may beapproximately 8×8 mm with a weight of less than 3 grams. A difference inoverall performance between the configuration illustrated in FIG. 3b andthe configuration illustrated in FIG. 4 is that the embodiment of FIG. 4doesn't require the use of polarized light as supplied by the lightsource 404. This can be an advantage in some situations as will bediscussed in more detail below (e.g. increased see-through transparencyof the HWC optics from the user's perspective). Polarized light may beused in connection with the embodiment depicted in FIG. 4, inembodiments. An additional advantage of the embodiment of FIG. 4compared to the embodiment shown in FIG. 3b is that the dark state light(shown as DLP off light 410) is directed at a steeper angle away fromthe optical axis of the image light 414 due to the added refractionencountered when the dark state light 410 exits the corrective wedge420. This steeper angle of the dark state light 410 allows for the lighttrap to be positioned closer to the DLP 402 so that the overall size ofthe upper module 202 can be reduced. The light trap can also be madelarger since the light trap doesn't interfere with the field lens,thereby the efficiency of the light trap can be increased and as aresult, stray light can be reduced and the contrast of the imageperceived by the user can be increased. FIG. 4a illustrates theembodiment described in connection with FIG. 4 with an example set ofcorresponding angles at the various surfaces with the reflected anglesof a ray of light passing through the upper optical module 202. In thisexample, the DLP mirrors are provided at 17 degrees to the surface ofthe DLP device. The angles of the TIR wedge are selected incorrespondence to one another to provide TIR reflected illuminationlight at the correct angle for the DLP mirrors while allowing the imagelight and dark state light to pass through the thin air gap, variouscombinations of angles are possible to achieve this.

FIG. 5 illustrates yet another embodiment of an upper optical module 202in accordance with the principles of the present invention. As with theembodiment shown in FIG. 4, the embodiment shown in FIG. 5 does notrequire the use of polarized light. Polarized light may be used inconnection with this embodiment, but it is not required. The opticalmodule 202 depicted in FIG. 5 is similar to that presented in connectionwith FIG. 4; however, the embodiment of FIG. 5 includes an off lightredirection wedge 502. As can be seen from the illustration, the offlight redirection wedge 502 allows the image light 414 to continuegenerally along the optical axis toward the field lens and into thelower optical module 204 (as illustrated). However, the off light 504 isredirected substantially toward the side of the corrective wedge 420where it passes into the light trap. This configuration may allowfurther height compactness in the HWC because the light trap (notillustrated) that is intended to absorb the off light 504 can bepositioned laterally adjacent the upper optical module 202 as opposed tobelow it. In the embodiment depicted in FIG. 5 there is a thin air gapbetween the TIR wedge 418 and the corrective wedge 420 (similar to theembodiment of FIG. 4). There is also a thin air gap between thecorrective wedge 420 and the off light redirection wedge 502. There maybe HWC mechanical configurations that warrant the positioning of a lighttrap for the dark state light elsewhere and the illustration depicted inFIG. 5 should be considered illustrative of the concept that the offlight can be redirected to create compactness of the overall HWC. FIG.5a illustrates an example of the embodiment described in connection withFIG. 5 with the addition of more details on the relative angles at thevarious surfaces and a light ray trace for image light and a light raytrace for dark light are shown as it passes through the upper opticalmodule 202. Again, various combinations of angles are possible.

FIG. 4b shows an illustration of a further embodiment in which a solidtransparent matched set of wedges 456 is provided with a reflectivepolarizer 450 at the interface between the wedges. Wherein the interfacebetween the wedges in the wedge set 456 is provided at an angle so thatillumination light 452 from the polarized light source 458 is reflectedat the proper angle (e.g. 34 degrees for a 17 degree DLP mirror) for theDLP mirror “on” state so that the reflected image light 414 is providedalong the optical axis of the field lens. The general geometry of thewedges in the wedge set 456 is similar to that shown in FIGS. 4 and 4 a.A quarter wave film 454 is provided on the DLP 402 surface so that theillumination light 452 is one polarization state (e.g. S polarizationstate) while in passing through the quarter wave film 454, reflectingfrom the DLP mirror and passing back through the quarter wave film 454,the image light 414 is converted to the other polarization state (e.g. Ppolarization state). The reflective polarizer is oriented such that theillumination light 452 with its polarization state is reflected and theimage light 414 with its other polarization state is transmitted. Sincethe dark state light from the “off” pixels 410 also passes through thequarter wave film 454 twice, it is also the other polarization state(e.g. P polarization state) so that it is transmitted by the reflectivepolarizer 450.

The angles of the faces of the wedge set 450 correspond to the neededangles to provide illumination light 452 at the angle needed by the DLPmirrors when in the “on” state so that the reflected image light 414 isreflected from the DLP along the optical axis of the field lens. Thewedge set 456 provides an interior interface where a reflectivepolarizer film can be located to redirect the illumination light 452toward the mirrors of the DLP 402. The wedge set also provides a matchedwedge on the opposite side of the reflective polarizer 450 so that theimage light 414 from the “on” pixels exits the wedge set 450substantially perpendicular to the exit surface, while the dark statelight from the ‘off pixels 410 exits at an oblique angle to the exitsurface. As a result, the image light 414 is substantially unrefractedupon exiting the wedge set 456, while the dark state light from the“off” pixels 410 is substantially refracted upon exiting the wedge set456 as shown in FIG. 4 b.

By providing a solid transparent matched wedge set, the flatness of theinterface is reduced, because variations in the flatness have anegligible effect as long as they are within the cone angle of theilluminating light 452. Which can be f #2.2 with a 26 degree cone angle.In a preferred embodiment, the reflective polarizer is bonded betweenthe matched internal surfaces of the wedge set 456 using an opticaladhesive so that Fresnel reflections at the interfaces on either side ofthe reflective polarizer 450 are reduced. The optical adhesive can bematched in refractive index to the material of the wedge set 456 and thepieces of the wedge set 456 can be all made from the same material suchas BK7 glass or cast acrylic. Wherein the wedge material can be selectedto have low birefringence as well to reduce non-uniformities inbrightness. The wedge set 456 and the quarter wave film 454 can also bebonded to the DLP 402 to further reduce Fresnel reflections at the DLPinterface losses. In addition, since the image light 414 issubstantially normal to the exit surface of the wedge set 456, theflatness of the surface is not critical to maintain the wavefront of theimage light 414 so that high image quality can be obtained in thedisplayed image without requiring very tightly toleranced flatness onthe exit surface.

A yet further embodiment of the invention that is not illustrated,combines the embodiments illustrated in FIG. 4b and FIG. 5. In thisembodiment, the wedge set 456 is comprised of three wedges with thegeneral geometry of the wedges in the wedge set corresponding to thatshown in FIGS. 5 and 5 a. A reflective polarizer is bonded between thefirst and second wedges similar to that shown in FIG. 4b , however, athird wedge is provided similar to the embodiment of FIG. 5. Whereinthere is an angled thin air gap between the second and third wedges sothat the dark state light is reflected by TIR toward the side of thesecond wedge where it is absorbed in a light trap. This embodiment, likethe embodiment shown in FIG. 4b , uses a polarized light source as hasbeen previously described. The difference in this embodiment is that theimage light is transmitted through the reflective polarizer and istransmitted through the angled thin air gap so that it exits normal tothe exit surface of the third wedge.

FIG. 5b illustrates an upper optical module 202 with a dark light trap514 a. As described in connection with FIGS. 4 and 4 a, image light canbe generated from a DLP when using a TIR and corrective lensconfiguration. The upper module may be mounted in a HWC housing 510 andthe housing 510 may include a dark light trap 514 a. The dark light trap514 a is generally positioned/constructed/formed in a position that isoptically aligned with the dark light optical axis 512. As illustrated,the dark light trap may have depth such that the trap internallyreflects dark light in an attempt to further absorb the light andprevent the dark light from combining with the image light that passesthrough the field lens. The dark light trap may be of a shape and depthsuch that it absorbs the dark light. In addition, the dark light trap514 b, in embodiments, may be made of light absorbing materials orcoated with light absorbing materials. In embodiments, the recessedlight trap 514 a may include baffles to block a view of the dark statelight. This may be combined with black surfaces and textured or fibroussurfaces to help absorb the light. The baffles can be part of the lighttrap, associated with the housing, or field lens, etc.

FIG. 5c illustrates another embodiment with a light trap 514 b. As canbe seen in the illustration, the shape of the trap is configured toenhance internal reflections within the light trap 514 b to increase theabsorption of the dark light 512. FIG. 5d illustrates another embodimentwith a light trap 514 c. As can be seen in the illustration, the shapeof the trap 514 c is configured to enhance internal reflections toincrease the absorption of the dark light 512.

FIG. 5e illustrates another embodiment of an upper optical module 202with a dark light trap 514 d. This embodiment of upper module 202includes an off light reflection wedge 502, as illustrated and describedin connection with the embodiment of FIGS. 5 and 5 a. As can be seen inFIG. 5e , the light trap 514 d is positioned along the optical path ofthe dark light 512. The dark light trap 514 d may be configured asdescribed in other embodiments herein. The embodiment of the light trap514 d illustrated in FIG. 5e includes a black area on the side wall ofthe wedge, wherein the side wall is located substantially away from theoptical axis of the image light 414. In addition, baffles 5252 may beadded to one or more edges of the field lens 312 to block the view ofthe light trap 514 d adjacent to the displayed image seen by the user.

FIG. 6 illustrates a combination of an upper optical module 202 with alower optical module 204. In this embodiment, the image light projectedfrom the upper optical module 202 may or may not be polarized. The imagelight is reflected off a flat combiner element 602 such that it isdirected towards the user's eye. Wherein, the combiner element 602 is apartial mirror that reflects image light while transmitting asubstantial portion of light from the environment so the user can lookthrough the combiner element and see the environment surrounding theHWC.

The combiner 602 may include a holographic pattern, to form aholographic mirror. If a monochrome image is desired, there may be asingle wavelength reflection design for the holographic pattern on thesurface of the combiner 602. If the intention is to have multiple colorsreflected from the surface of the combiner 602, a multiple wavelengthholographic mirror maybe included on the combiner surface. For example,in a three-color embodiment, where red, green and blue pixels aregenerated in the image light, the holographic mirror may be reflectiveto wavelengths substantially matching the wavelengths of the red, greenand blue light provided by the light source. This configuration can beused as a wavelength specific mirror where pre-determined wavelengths oflight from the image light are reflected to the user's eye. Thisconfiguration may also be made such that substantially all otherwavelengths in the visible pass through the combiner element 602 so theuser has a substantially clear view of the surroundings when lookingthrough the combiner element 602. The transparency between the user'seye and the surrounding may be approximately 80% when using a combinerthat is a holographic mirror. Wherein holographic mirrors can be madeusing lasers to produce interference patterns in the holographicmaterial of the combiner where the wavelengths of the lasers correspondto the wavelengths of light that are subsequently reflected by theholographic mirror.

In another embodiment, the combiner element 602 may include a notchmirror comprised of a multilayer coated substrate wherein the coating isdesigned to substantially reflect the wavelengths of light provided bythe light source and substantially transmit the remaining wavelengths inthe visible spectrum. For example, in the case where red, green and bluelight is provided by the light source to enable full color images to beprovided to the user, the notch mirror is a tristimulus notch mirrorwherein the multilayer coating is designed to reflect narrow bands ofred, green and blue light that are matched to what is provided by thelight source and the remaining visible wavelengths are transmittedthrough the coating to enable a view of the environment through thecombiner. In another example where monochrome images are provided to theuser, the notch mirror is designed to reflect a single narrow band oflight that is matched to the wavelength range of the light provided bythe light source while transmitting the remaining visible wavelengths toenable a see-thru view of the environment. The combiner 602 with thenotch mirror would operate, from the user's perspective, in a mannersimilar to the combiner that includes a holographic pattern on thecombiner element 602. The combiner, with the tristimulus notch mirror,would reflect the “on” pixels to the eye because of the match betweenthe reflective wavelengths of the notch mirror and the color of theimage light, and the wearer would be able to see with high clarity thesurroundings. The transparency between the user's eye and thesurrounding may be approximately 80% when using the tristimulus notchmirror. In addition, the image provided by the upper optical module 202with the notch mirror combiner can provide higher contrast images thanthe holographic mirror combiner due to less scattering of the imaginglight by the combiner.

Light can escape through the combiner 602 and may produce face glow asthe light is generally directed downward onto the cheek of the user.When using a holographic mirror combiner or a tristimulus notch mirrorcombiner, the escaping light can be trapped to avoid face glow. Inembodiments, if the image light is polarized before the combiner, alinear polarizer can be laminated, or otherwise associated, to thecombiner, with the transmission axis of the polarizer oriented relativeto the polarized image light so that any escaping image light isabsorbed by the polarizer. In embodiments, the image light would bepolarized to provide S polarized light to the combiner for betterreflection. As a result, the linear polarizer on the combiner would beoriented to absorb S polarized light and pass P polarized light. Thisprovides the preferred orientation of polarized sunglasses as well.

If the image light is unpolarized, a microlouvered film such as aprivacy filter can be used to absorb the escaping image light whileproviding the user with a see-thru view of the environment. In thiscase, the absorbance or transmittance of the microlouvered film isdependent on the angle of the light. Where steep angle light is absorbedand light at less of an angle is transmitted. For this reason, in anembodiment, the combiner with the microlouver film is angled at greaterthan 45 degrees to the optical axis of the image light (e.g. thecombiner can be oriented at 50 degrees so the image light from the filelens is incident on the combiner at an oblique angle).

FIG. 7 illustrates an embodiment of a combiner element 602 at variousangles when the combiner element 602 includes a holographic mirror.Normally, a mirrored surface reflects light at an angle equal to theangle that the light is incident to the mirrored surface. Typically,this necessitates that the combiner element be at 45 degrees, 602 a, ifthe light is presented vertically to the combiner so the light can bereflected horizontally towards the wearer's eye. In embodiments, theincident light can be presented at angles other than vertical to enablethe mirror surface to be oriented at other than 45 degrees, but in allcases wherein a mirrored surface is employed (including the tristimulusnotch mirror described previously), the incident angle equals thereflected angle. As a result, increasing the angle of the combiner 602 arequires that the incident image light be presented to the combiner 602a at a different angle which positions the upper optical module 202 tothe left of the combiner as shown in FIG. 7. In contrast, a holographicmirror combiner, included in embodiments, can be made such that light isreflected at a different angle from the angle that the light is incidentonto the holographic mirrored surface. This allows freedom to select theangle of the combiner element 602 b independent of the angle of theincident image light and the angle of the light reflected into thewearer's eye. In embodiments, the angle of the combiner element 602 b isgreater than 45 degrees (shown in FIG. 7) as this allows a morelaterally compact HWC design. The increased angle of the combinerelement 602 b decreases the front to back width of the lower opticalmodule 204 and may allow for a thinner HWC display (i.e. the furthestelement from the wearer's eye can be closer to the wearer's face).

FIG. 8 illustrates another embodiment of a lower optical module 204. Inthis embodiment, polarized image light provided by the upper opticalmodule 202, is directed into the lower optical module 204. The imagelight reflects off a polarized mirror 804 and is directed to a focusingpartially reflective mirror 802, which is adapted to reflect thepolarized light. An optical element such as a ¼ wave film locatedbetween the polarized mirror 804 and the partially reflective mirror802, is used to change the polarization state of the image light suchthat the light reflected by the partially reflective mirror 802 istransmitted by the polarized mirror 804 to present image light to theeye of the wearer. The user can also see through the polarized mirror804 and the partially reflective mirror 802 to see the surroundingenvironment. As a result, the user perceives a combined image comprisedof the displayed image light overlaid onto the see-thru view of theenvironment.

While many of the embodiments of the present invention have beenreferred to as upper and lower modules containing certain opticalcomponents, it should be understood that the image light and dark lightproduction and management functions described in connection with theupper module may be arranged to direct light in other directions (e.g.upward, sideward, etc.). In embodiments, it may be preferred to mountthe upper module 202 above the wearer's eye, in which case the imagelight would be directed downward. In other embodiments it may bepreferred to produce light from the side of the wearer's eye, or frombelow the wearer's eye. In addition, the lower optical module isgenerally configured to deliver the image light to the wearer's eye andallow the wearer to see through the lower optical module, which may beaccomplished through a variety of optical components.

FIG. 8a illustrates an embodiment of the present invention where theupper optical module 202 is arranged to direct image light into a TIRwaveguide 810. In this embodiment, the upper optical module 202 ispositioned above the wearer's eye 812 and the light is directedhorizontally into the TIR waveguide 810. The TIR waveguide is designedto internally reflect the image light in a series of downward TIRreflections until it reaches the portion in front of the wearer's eye,where the light passes out of the TIR waveguide 812 into the wearer'seye. In this embodiment, an outer shield 814 is positioned in front ofthe TIR waveguide 810.

FIG. 8b illustrates an embodiment of the present invention where theupper optical module 202 is arranged to direct image light into a TIRwaveguide 818. In this embodiment, the upper optical module 202 isarranged on the side of the TIR waveguide 818. For example, the upperoptical module may be positioned in the arm or near the arm of the HWCwhen configured as a pair of head worn glasses. The TIR waveguide 818 isdesigned to internally reflect the image light in a series of TIRreflections until it reaches the portion in front of the wearer's eye,where the light passes out of the TIR waveguide 812 into the wearer'seye.

FIG. 8c illustrates yet further embodiments of the present inventionwhere an upper optical module 202 is directing polarized image lightinto an optical guide 828 where the image light passes through apolarized reflector 824, changes polarization state upon reflection ofthe optical element 822 which includes a ¼ wave film for example andthen is reflected by the polarized reflector 824 towards the wearer'seye, due to the change in polarization of the image light. The upperoptical module 202 may be positioned to direct light to a mirror 820, toposition the upper optical module 202 laterally, in other embodiments,the upper optical module 202 may direct the image light directly towardsthe polarized reflector 824. It should be understood that the presentinvention comprises other optical arrangements intended to direct imagelight into the wearer's eye.

Another aspect of the present invention relates to eye imaging. Inembodiments, a camera is used in connection with an upper optical module202 such that the wearer's eye can be imaged using pixels in the “off”state on the DLP. FIG. 9 illustrates a system where the eye imagingcamera 802 is mounted and angled such that the field of view of the eyeimaging camera 802 is redirected toward the wearer's eye by the mirrorpixels of the DLP 402 that are in the “off” state. In this way, the eyeimaging camera 802 can be used to image the wearer's eye along the sameoptical axis as the displayed image that is presented to the wearer.Wherein, image light that is presented to the wearer's eye illuminatesthe wearer's eye so that the eye can be imaged by the eye imaging camera802. In the process, the light reflected by the eye passes back thoughthe optical train of the lower optical module 204 and a portion of theupper optical module to where the light is reflected by the “off” pixelsof the DLP 402 toward the eye imaging camera 802.

In embodiments, the eye imaging camera may image the wearer's eye at amoment in time where there are enough “off” pixels to achieve therequired eye image resolution. In another embodiment, the eye imagingcamera collects eye image information from “off” pixels over time andforms a time lapsed image. In another embodiment, a modified image ispresented to the user wherein enough “off” state pixels are includedthat the camera can obtain the desired resolution and brightness forimaging the wearer's eye and the eye image capture is synchronized withthe presentation of the modified image.

The eye imaging system may be used for security systems. The HWC may notallow access to the HWC or other system if the eye is not recognized(e.g. through eye characteristics including retina or irischaracteristics, etc.). The HWC may be used to provide constant securityaccess in some embodiments. For example, the eye security confirmationmay be a continuous, near-continuous, real-time, quasi real-time,periodic, etc. process so the wearer is effectively constantly beingverified as known. In embodiments, the HWC may be worn and eye securitytracked for access to other computer systems.

The eye imaging system may be used for control of the HWC. For example,a blink, wink, or particular eye movement may be used as a controlmechanism for a software application operating on the HWC or associateddevice.

The eye imaging system may be used in a process that determines how orwhen the HWC 102 delivers digitally displayed content to the wearer. Forexample, the eye imaging system may determine that the user is lookingin a direction and then HWC may change the resolution in an area of thedisplay or provide some content that is associated with something in theenvironment that the user may be looking at. Alternatively, the eyeimaging system may identify different user's and change the displayedcontent or enabled features provided to the user. User's may beidentified from a database of users eye characteristics either locatedon the HWC 102 or remotely located on the network 110 or on a server112. In addition, the HWC may identify a primary user or a group ofprimary users from eye characteristics wherein the primary user(s) areprovided with an enhanced set of features and all other users areprovided with a different set of features. Thus in this use case, theHWC 102 uses identified eye characteristics to either enable features ornot and eye characteristics need only be analyzed in comparison to arelatively small database of individual eye characteristics.

FIG. 10 illustrates a light source that may be used in association withthe upper optics module 202 (e.g. polarized light source if the lightfrom the solid state light source is polarized such as polarized lightsource 302 and 458), and light source 404. In embodiments, to provide auniform surface of light 1008 to be directed into the upper opticalmodule 202 and towards the DLP of the upper optical module, eitherdirectly or indirectly, the solid state light source 1002 may beprojected into a backlighting optical system 1004. The solid state lightsource 1002 may be one or more LEDs, laser diodes, OLEDs. Inembodiments, the backlighting optical system 1004 includes an extendedsection with a length/distance ratio of greater than 3, wherein thelight undergoes multiple reflections from the sidewalls to mix ofhomogenize the light as supplied by the solid state light source 1002.The backlighting optical system 1004 can also include structures on thesurface opposite (on the left side as shown in FIG. 10) to where theuniform light 1008 exits the backlight 1004 to change the direction ofthe light toward the DLP 302 and the reflective polarizer 310 or the DLP402 and the TIR wedge 418. The backlighting optical system 1004 may alsoinclude structures to collimate the uniform light 1008 to provide lightto the DLP with a smaller angular distribution or narrower cone angle.Diffusers or polarizers can be used on the entrance or exit surface ofthe backlighting optical system. Diffusers can be used to spread oruniformize the exiting light from the backlight to improve theuniformity or increase the angular spread of the uniform light 1008.Elliptical diffusers that diffuse the light more in some directions andless in others can be used to improve the uniformity or spread of theuniform light 1008 in directions orthogonal to the optical axis of theuniform light 1008. Linear polarizers can be used to convert unpolarizedlight as supplied by the solid state light source 1002 to polarizedlight so the uniform light 1008 is polarized with a desired polarizationstate. A reflective polarizer can be used on the exit surface of thebacklight 1004 to polarize the uniform light 1008 to the desiredpolarization state, while reflecting the other polarization state backinto the backlight where it is recycled by multiple reflections withinthe backlight 1004 and at the solid state light source 1002. Thereforeby including a reflective polarizer at the exit surface of the backlight1004, the efficiency of the polarized light source is improved.

FIGS. 10a and 10b show illustrations of structures in backlight opticalsystems 1004 that can be used to change the direction of the lightprovided to the entrance face 1045 by the light source and thencollimates the light in a direction lateral to the optical axis of theexiting uniform light 1008. Structure 1060 includes an angled sawtoothpattern in a transparent waveguide wherein the left edge of eachsawtooth clips the steep angle rays of light thereby limiting the angleof the light being redirected. The steep surface at the right (as shown)of each sawtooth then redirects the light so that it reflects off theleft angled surface of each sawtooth and is directed toward the exitsurface 1040. The sawtooth surfaces shown on the lower surface in FIGS.10a and 10b , can be smooth and coated (e.g. with an aluminum coating ora dielectric mirror coating) to provide a high level of reflectivitywithout scattering. Structure 1050 includes a curved face on the leftside (as shown) to focus the rays after they pass through the exitsurface 1040, thereby providing a mechanism for collimating the uniformlight 1008. In a further embodiment, a diffuser can be provided betweenthe solid state light source 1002 and the entrance face 1045 tohomogenize the light provided by the solid state light source 1002. Inyet a further embodiment, a polarizer can be used between the diffuserand the entrance face 1045 of the backlight 1004 to provide a polarizedlight source. Because the sawtooth pattern provides smooth reflectivesurfaces, the polarization state of the light can be preserved from theentrance face 1045 to the exit face 1040. In this embodiment, the lightentering the backlight from the solid state light source 1002 passesthrough the polarizer so that it is polarized with the desiredpolarization state. If the polarizer is an absorptive linear polarizer,the light of the desired polarization state is transmitted while thelight of the other polarization state is absorbed. If the polarizer is areflective polarizer, the light of the desired polarization state istransmitted into the backlight 1004 while the light of the otherpolarization state is reflected back into the solid state light source1002 where it can be recycled as previously described, to increase theefficiency of the polarized light source.

FIG. 11a illustrates a light source 1100 that may be used in associationwith the upper optics module 202. In embodiments, the light source 1100may provide light to a backlighting optical system 1004 as describedabove in connection with FIG. 10. In embodiments, the light source 1100includes a tristimulus notch filter 1102. The tristimulus notch filter1102 has narrow band pass filters for three wavelengths, as indicated inFIG. 11c in a transmission graph 1108. The graph shown in FIG. 11b , as1104 illustrates an output of three different colored LEDs. One can seethat the bandwidths of emission are narrow, but they have long tails.The tristimulus notch filter 1102 can be used in connection with suchLEDs to provide a light source 1100 that emits narrow filteredwavelengths of light as shown in FIG. 11d as the transmission graph1110. Wherein the clipping effects of the tristimulus notch filter 1102can be seen to have cut the tails from the LED emission graph 1104 toprovide narrower wavelength bands of light to the upper optical module202. The light source 1100 can be used in connection with a combiner 602with a holographic mirror or tristimulus notch mirror to provide narrowhands of light that are reflected toward the wearer's eye with lesswaste light that does not get reflected by the combiner, therebyimproving efficiency and reducing escaping light that can causefaceglow.

FIG. 12a illustrates another light source 1200 that may be used inassociation with the upper optics module 202. In embodiments, the lightsource 1200 may provide light to a backlighting optical system 1004 asdescribed above in connection with FIG. 10. In embodiments, the lightsource 1200 includes a quantum dot cover glass 1202. Where the quantumdots absorb light of a shorter wavelength and emit light of a longerwavelength (FIG. 12b shows an example wherein a UV spectrum 1202 appliedto a quantum dot results in the quantum dot emitting a narrow band shownas a PL spectrum 1204) that is dependent on the material makeup and sizeof the quantum dot. As a result, quantum dots in the quantum dot coverglass 1202 can be tailored to provide one or more bands of narrowbandwidth light (e.g. red, green and blue emissions) dependent on thedifferent quantum dots included as illustrated in the graph shown inFIG. 12c where three different quantum dots are used. In embodiments,the LED driver light emits UV light, deep blue or blue light. Forsequential illumination of different colors, multiple light sources 1200would be used where each light source 1200 would include a quantum dotcover glass 1202 with a quantum dot selected to emit at one of thedesired colors. The light source 1100 can be used in connection with acombiner 602 with a holographic mirror or tristimulus notch mirror toprovide narrow transmission bands of light that are reflected toward thewearer's eye with less waste light that does not get reflected.

Another aspect of the present invention relates to the generation ofperipheral image lighting effects for a person wearing a HWC. Inembodiments, a solid state lighting system (e.g. LED, OLED, etc), orother lighting system, may be included inside the optical elements of alower optical module 204. The solid state lighting system may bearranged such that lighting effects outside of a field of view (FOV) ofthe presented digital content is presented to create an immersive effectfor the person wearing the HWC. To this end, the lighting effects may bepresented to any portion of the HWC that is visible to the wearer. Thesolid state lighting system may be digitally controlled by an integratedprocessor on the HWC. In embodiments, the integrated processor willcontrol the lighting effects in coordination with digital content thatis presented within the FOV of the HWC. For example, a movie, picture,game, or other content, may be displayed or playing within the FOV ofthe HWC. The content may show a bomb blast on the right side of the FOVand at the same moment, the solid state lighting system inside of theupper module optics may flash quickly in concert with the FOV imageeffect. The effect may not be fast, it may be more persistent toindicate, for example, a general glow or color on one side of the user.The solid state lighting system may be color controlled, with red, greenand blue LEDs, for example, such that color control can be coordinatedwith the digitally presented content within the field of view.

FIG. 13a illustrates optical components of a lower optical module 204together with an outer lens 1302. FIG. 13a also shows an embodimentincluding effects LED's 1308 a and 1308 b. FIG. 13a illustrates imagelight 1312, as described herein elsewhere, directed into the upperoptical module where it will reflect off of the combiner element 1304,as described herein elsewhere. The combiner element 1304 in thisembodiment is angled towards the wearer's eye at the top of the moduleand away from the wearer's eye at the bottom of the module, as alsoillustrated and described in connection with FIG. 8 (e.g. at a 45 degreeangle). The image light 1312 provided by an upper optical module 202(not shown in FIG. 13a ) reflects off of the combiner element 1304towards the collimating mirror 1310, away from the wearer's eye, asdescribed herein elsewhere. The image light 1312 then reflects andfocuses off of the collimating mirror 1304, passes back through thecombiner element 1304, and is directed into the wearer's eye. The wearercan also view the surrounding environment through the transparency ofthe combiner element 1304, collimating mirror 1310, and outer lens 1302(if it is included). As described herein elsewhere, various surfaces arepolarized to create the optical path for the image light and to providetransparency of the elements such that the wearer can view thesurrounding environment. The wearer will generally perceive that theimage light forms an image in the FOV 1305. In embodiments, the outerlens 1302 may be included. The outer lens 1302 is an outer lens that mayor may not be corrective and it may be designed to conceal the loweroptical module components in an effort to make the HWC appear to be in aform similar to standard glasses or sunglasses.

In the embodiment illustrated in FIG. 13a , the effects LEDs 1308 a and1308 b are positioned at the sides of the combiner element 1304 and theouter lens 1302 and/or the collimating mirror 1310. In embodiments, theeffects LEDs 1308 a are positioned within the confines defined by thecombiner element 1304 and the outer lens 1302 and/or the collimatingmirror. The effects LEDs 1308 a and 1308 b are also positioned outsideof the FOV 1305. In this arrangement, the effects LEDs 1308 a and 1308 bcan provide lighting effects within the lower optical module outside ofthe FOV 1305. In embodiments the light emitted from the effects LEDs1308 a and 1308 b may be polarized such that the light passes throughthe combiner element 1304 toward the wearer's eye and does not passthrough the outer lens 1302 and/or the collimating mirror 1310. Thisarrangement provides peripheral lighting effects to the wearer in a moreprivate setting by not transmitting the lighting effects through thefront of the HWC into the surrounding environment. However, in otherembodiments, the effects LEDs 1308 a and 1308 b may be unpolarized sothe lighting effects provided are made to be purposefully viewable byothers in the environment for entertainment such as giving the effect ofthe wearer's eye glowing in correspondence to the image content beingviewed by the wearer.

FIG. 13b illustrates a cross section of the embodiment described inconnection with FIG. 13a . As illustrated, the effects LED 1308 a islocated in the upper-front area inside of the optical components of thelower optical module. It should be understood that the effects LED 1308a position in the described embodiments is only illustrative andalternate placements are encompassed by the present invention.Additionally, in embodiments, there may be one or more effects LEDs 1308a in each of the two sides of HWC to provide peripheral lighting effectsnear one or both eyes of the wearer.

FIG. 13c illustrates an embodiment where the combiner element 1304 isangled away from the eye at the top and towards the eye at the bottom(e.g. in accordance with the holographic or notch filter embodimentsdescribed herein). In this embodiment, the effects LED 1308 a is locatedon the outer lens 1302 side of the combiner element 1304 to provide aconcealed appearance of the lighting effects. As with other embodiments,the effects LED 1308 a of FIG. 13c may include a polarizer such that theemitted light can pass through a polarized element associated with thecombiner element 1304 and be blocked by a polarized element associatedwith the outer lens 1302.

Another aspect of the present invention relates to the mitigation oflight escaping from the space between the wearer's face and the HWCitself. Another aspect of the present invention relates to maintaining acontrolled lighting environment in proximity to the wearer's eyes. Inembodiments, both the maintenance of the lighting environment and themitigation of light escape are accomplished by including a removable andreplaceable flexible shield for the HWC. Wherein the removable andreplaceable shield can be provided for one eye or both eyes incorrespondence to the use of the displays for each eye. For example, ina night vision application, the display to only one eye could be usedfor night vision while the display to the other eye is turned off toprovide good see-thru when moving between areas where visible light isavailable and dark areas where night vision enhancement is needed.

FIG. 14a illustrates a removable and replaceable flexible eye cover 1402with an opening 1408 that can be attached and removed quickly from theHWC 102 through the use of magnets 1404. Other attachment methods may beused, but for illustration of the present invention we will focus on amagnet implementation. In embodiments, magnets may be included in theeye cover 1402 and magnets of an opposite polarity may be included (e.g.embedded) in the frame of the HWC 102. The magnets of the two elementswould attract quite strongly with the opposite polarity configuration.In another embodiment, one of the elements may have a magnet and theother side may have metal for the attraction. In embodiments, the eyecover 1402 is a flexible elastomeric shield. In embodiments, the eyecover 1402 may be an elastomeric bellows design to accommodateflexibility and more closely align with the wearer's face. FIG. 14billustrates a removable and replaceable flexible eye cover 1402 that isadapted as a single eye cover. In embodiments, a single eye cover may beused for each side of the HWC to cover both eyes of the wearer. Inembodiments, the single eye cover may be used in connection with a HWCthat includes only one computer display for one eye. Theseconfigurations prevent light that is generated and directed generallytowards the wearer's face by covering the space between the wearer'sface and the HWC. The opening 1408 allows the wearer to look through theopening 1408 to view the displayed content and the surroundingenvironment through the front of the HWC. The image light in the loweroptical module 204 can be prevented from emitting from the front of theHWC through internal optics polarization schemes, as described herein,for example.

FIG. 14c illustrates another embodiment of a light suppression system.In this embodiment, the eye cover 1410 may be similar to the eye cover1402, but eye cover 1410 includes a front light shield 1412. The frontlight shield 1412 may be opaque to prevent light from escaping the frontlens of the HWC. In other embodiments, the front light shield 1412 ispolarized to prevent light from escaping the front lens. In a polarizedarrangement, in embodiments, the internal optical elements of the HWC(e.g. of the lower optical module 204) may polarize light transmittedtowards the front of the HWC and the front light shield 1412 may bepolarized to prevent the light from transmitting through the front lightshield 1412.

In embodiments, an opaque front light shield 1412 may be included andthe digital content may include images of the surrounding environmentsuch that the wearer can visualize the surrounding environment. One eyemay be presented with night vision environmental imagery and this eye'ssurrounding environment optical path may be covered using an opaquefront light shield 1412. In other embodiments, this arrangement may beassociated with both eyes.

Another aspect of the present invention relates to automaticallyconfiguring the lighting system(s) used in the HWC 102. In embodiments,the display lighting and/or effects lighting, as described herein, maybe controlled in a manner suitable for when an eye cover 1402 isattached or removed from the HWC 102. For example, at night, when thelight in the environment is low, the lighting system(s) in the HWC maygo into a low light mode to further control any amounts of stray lightescaping from the HWC and the areas around the HWC. Covert operations atnight, while using night vision or standard vision, may require asolution which prevents as much escaping light as possible so a user mayclip on the eye cover(s) 1402 and then the HWC may go into a low lightmode. The low light mode may, in some embodiments, only go into a lowlight mode when the eye cover 1402 is attached if the HWC identifiesthat the environment is in low light conditions (e.g. throughenvironment light level sensor detection). In embodiments, the low lightlevel may be determined to be at an intermediate point between full andlow light dependent on environmental conditions.

Another aspect of the present invention relates to automaticallycontrolling the type of content displayed in the HWC when eye covers1402 are attached or removed from the HWC. In embodiments, when the eyecover(s) 1402 is attached to the HWC, the displayed content may berestricted in amount or in color amounts. For example, the display(s)may go into a simple content delivery mode to restrict the amount ofinformation displayed. This may be done to reduce the amount of lightproduced by the display(s). In an embodiment, the display(s) may changefrom color displays to monochrome displays to reduce the amount of lightproduced. In an embodiment, the monochrome lighting may be red to limitthe impact on the wearer's eyes to maintain an ability to see better inthe dark.

Another aspect of the present invention relates to a system adapted toquickly convert from a see-through system to a non-see-through or verylow transmission see-through system for a more immersive userexperience. The conversion system may include replaceable lenses, an eyecover, and optics adapted to provide user experiences in both modes. Thelenses, for example, may be ‘blacked-out’ to provide an experience whereall of the user's attention is dedicated to the digital content and thenthe lenses may be switched out for high see-through lenses so thedigital content is augmenting the user's view of the surroundingenvironment. Another aspect of the invention relates to low transmissionlenses that permit the user to see through the lenses but remain darkenough to maintain most of the user's attention on the digital content.The slight see-through can provide the user with a visual connection tothe surrounding environment and this can reduce or eliminate nausea andother problems associated with total removal of the surrounding viewwhen viewing digital content.

FIG. 14d illustrates a head-worn computer system 102 with a see-throughdigital content display 204 adapted to include a removable outer lens1414 and a removable eye cover 1402. The eye cover 1402 may be attachedto the head-worn computer 102 with magnets 1404 or other attachmentsystems (e.g. mechanical attachments, a snug friction fit between thearms of the head-worn computer 102, etc.). The eye cover 1402 may beattached when the user wants to cut stray light from escaping theconfines of the head-worn computer, create a more immersive experienceby removing the otherwise viewable peripheral view of the surroundingenvironment, etc. The removable outer lens may be of several varietiesfor various experiences. It may have no transmission or a very lowtransmission to create a dark background for the digital content,creating an immersive experience for the digital content. It may have ahigh transmission so the user can see through the see-through displayand the lens to view the surrounding environment, creating a system fora heads-up display, augmented reality display, assisted reality display,etc. The lens 1414 may be dark in a middle portion to provide a darkbackground for the digital content (i.e. dark backdrop behind thesee-through field of view from the user's perspective) and a highertransmission area elsewhere. The lenses 1414 may have a transmission inthe range of 2 to 5%, 5 to 10%, 10 to 20% for the immersion effect andabove 10% or 20% for the augmented reality effect, for example. Thelenses 1414 may also have an adjustable transmission to facilitate thechange in system effect. For example, the lenses 1414 may beelectronically adjustable tint lenses (e.g. liquid crystal or havecrossed polarizers with an adjustment for the level of cross).

In embodiments, the eye cover may have areas of transparency or partialtransparency to provide some visual connection with the user'ssurrounding environment. This may also reduce or eliminate nausea orother feelings associated with the complete removal of the view of thesurrounding environment.

FIG. 14e illustrates a head-worn computer 102 assembled with an eyecover 1402 without lenses in place. The lenses, in embodiments, may beheld in place with magnets 1418 for ease of removal and replacement. Inembodiments, the lenses may be held in place with other systems, such asmechanical systems.

Another aspect of the present invention relates to an effects systemthat generates effects outside of the field of view in the see-throughdisplay of the head-worn computer. The effects may be, for example,lighting effects, sound effects, tactile effects (e.g. throughvibration), air movement effects, etc. In embodiments, the effectgeneration system is mounted on the eye cover 1402. For example, alighting system (e.g. LED(s), OLEDs, etc.) may be mounted on an insidesurface 1420, or exposed through the inside surface 1420, as illustratedin FIG. 14f , such that they can create a lighting effect (e.g. a brightlight, colored light, subtle color effect) in coordination with contentbeing displayed in the field of view of the see-through display. Thecontent may be a movie or a game, for example, and an explosion mayhappen on the right side of the content, as scripted, and matching thecontent, a bright flash may be generated by the effects lighting systemto create a stronger effect. As another example, the effects system mayinclude a vibratory system mounted near the sides or temples, orotherwise, and when the same explosion occurs, the vibratory system maygenerate a vibration on the right side to increase the user experienceindicating that the explosion had a real sound wave creating thevibration. As yet a further example, the effects system may have an airsystem where the effect is a puff of air blown onto the user's face.This may create a feeling of closeness with some fast moving object inthe content. The effects system may also have speakers directed towardsthe user's ears or an attachment for ear buds, etc.

In embodiments, the effects generated by the effects system may bescripted by an author to coordinate with the content. In embodiments,sensors may be placed inside of the eye cover to monitor content effects(e.g. a light sensor to measure strong lighting effects or peripherallighting effects) that would than cause an effect(s) to be generated.

The effects system in the eye cover may be powered by an internalbattery and the battery, in embodiments, may also provide additionalpower to the head-worn computer 102 as a back-up system. In embodiments,the effects system is powered by the batteries in the head-worncomputer. Power may be delivered through the attachment system (e.g.magnets, mechanical system) or a dedicated power system.

The effects system may receive data and/or commands from the head-worncomputer through a data connection that is wired or wireless. The datamay come through the attachment system, a separate line, or throughBluetooth or other short range communication protocol, for example.

In embodiments, the eye cover is made of reticulated foam, which is verylight and can contour to the user's face. The reticulated foam alsoallows air to circulate because of the open-celled nature of thematerial, which can reduce user fatigue and increase user comfort. Theeye cover may be made of other materials, soft, stiff, pliable, etc. andmay have another material on the periphery that contacts the face forcomfort. In embodiments, the eye cover may include a fan to exchange airbetween an external environment and an internal space, where theinternal space is defined in part by the face of the user. The fan mayoperate very slowly and at low power to exchange the air to keep theface of the user cool. In embodiments the fan may have a variable speedcontroller and/or a temperature sensor may be positioned to measuretemperature in the internal space to control the temperature in theinternal space to a specified range, temperature, etc. The internalspace is generally characterized by the space confined space in front ofthe user's eyes and upper cheeks where the eye cover encloses the area.

Another aspect of the present invention relates to flexibly mounting anaudio headset on the head-worn computer 102 and/or the eye cover 1402.In embodiments, the audio headset is mounted with a relatively rigidsystem that has flexible joint(s) (e.g. a rotational joint at theconnection with the eye cover, a rotational joint in the middle of arigid arm, etc.) and extension(s) (e.g. a telescopic arm) to provide theuser with adjustability to allow for a comfortable fit over, in oraround the user's ear. In embodiments, the audio headset is mounted witha flexible system that is more flexible throughout, such as with awire-based connection.

FIG. 14g illustrates a head-worn computer 102 with removable lenses 1414along with a mounted eye cover 1402. The head-worn computer, inembodiments, includes a see-through display (as disclosed herein). Theeye cover 1402 also includes a mounted audio headset 1422. The mountedaudio headset 1422 in this embodiment is mounted to the eye cover 1402and has audio wire connections (not shown). In embodiments, the audiowires' connections may connect to an internal wireless communicationsystem (e.g. Bluetooth, NFC, WiFi) to make connection to the processorin the head-worn computer. In embodiments, the audio wires may connectto a magnetic connector, mechanical connector or the like to make theconnection.

FIG. 14h illustrates an unmounted eye cover 1402 with a mounted audioheadset 1422. As illustrated, the mechanical design of the eye cover isadapted to fit onto the head-worn computer to provide visual isolationor partial isolation and the audio headset.

In embodiments, the eye cover 1402 may be adapted to be removablymounted on a head-worn computer 102 with a see-through computer display.An audio headset 1422 with an adjustable mount may be connected to theeye cover, wherein the adjustable mount may provide extension androtation to provide a user of the head-worn computer with a mechanism toalign the audio headset with an ear of the user. In embodiments, theaudio headset includes an audio wire connected to a connector on the eyecover and the eye cover connector may be adapted to removably mate witha connector on the head-worn computer. In embodiments, the audio headsetmay be adapted to receive audio signals from the head-worn computerthrough a wireless connection (e.g. Bluetooth, WiFi). As describedelsewhere herein, the head-worn computer may have a removable andreplaceable front lens. The eye cover may include a battery to powersystems internal to the eye cover. The eye cover may have a battery topower systems internal to the head-worn computer.

In embodiments, the eye cover may include a fan adapted to exchange airbetween an internal space, defined in part by the user's face, and anexternal environment to cool the air in the internal space and theuser's face. In embodiments, the audio headset may include a vibratorysystem (e.g. a vibration motor, piezo motor, etc. in the armature and/orin the section over the ear) adapted to provide the user with a hapticfeedback coordinated with digital content presented in the see-throughcomputer display. In embodiments, the head-worn computer includes avibratory system adapted to provide the user with a haptic feedbackcoordinated with digital content presented in the see-through computerdisplay.

In embodiments, the eye cover 1402 is adapted to be removably mounted ona head-worn computer with a see-through computer display. The eye covermay also include a flexible audio headset mounted to the eye cover,wherein the flexibility provides the user of the head-worn computer witha mechanism to align the audio headset with an ear of the user. Inembodiments, the flexible audio headset is mounted to the eye cover witha magnetic connection. In embodiments, the flexible audio headset may bemounted to the eye cover with a mechanical connection.

In embodiments, the audio head set may be spring or otherwise loadedsuch that the head set presses inward towards the user's ears for a moresecure fit.

Referring to FIG. 15, we now turn to describe a particular external userinterface 104, referred to generally as a pen 1500. The pen 1500 is aspecially designed external user interface 104 and can operate as a userinterface, such as to many different styles of HWC 102. The pen 1500generally follows the form of a conventional pen, which is a familiaruser handled device and creates an intuitive physical interface for manyof the operations to be carried out in the HWC system 100. The pen 1500may be one of several user interfaces 104 used in connection withcontrolling operations within the HWC system 100. For example, the HWC102 may watch for and interpret hand gestures 116 as control signals,where the pen 1500 may also be used as a user interface with the sameHWC 102. Similarly, a remote keyboard may be used as an external userinterface 104 in concert with the pen 1500. The combination of userinterfaces or the use of just one control system generally depends onthe operation(s) being executed in the HWC's system 100.

While the pen 1500 may follow the general form of a conventional pen, itcontains numerous technologies that enable it to function as an externaluser interface 104. FIG. 15 illustrates technologies comprised in thepen 1500. As can be seen, the pen 1500 may include a camera 1508, whichis arranged to view through lens 1502. The camera may then be focused,such as through lens 1502, to image a surface upon which a user iswriting or making other movements to interact with the HWC 102. Thereare situations where the pen 1500 will also have an ink, graphite, orother system such that what is being written can be seen on the writingsurface. There are other situations where the pen 1500 does not havesuch a physical writing system so there is no deposit on the writingsurface, where the pen would only be communicating data or commands tothe HWC 102. The lens configuration is described in greater detailherein. The function of the camera is to capture information from anunstructured writing surface such that pen strokes can be interpreted asintended by the user. To assist in the predication of the intendedstroke path, the pen 1500 may include a sensor, such as an IMU 1512. Ofcourse, the IMU could be included in the pen 1500 in its separate parts(e.g. gyro, accelerometer, etc.) or an IMU could be included as a singleunit. In this instance, the IMU 1512 is used to measure and predict themotion of the pen 1500. In turn, the integrated microprocessor 1510would take the IMU information and camera information as inputs andprocess the information to form a prediction of the pen tip movement.

The pen 1500 may also include a pressure monitoring system 1504, such asto measure the pressure exerted on the lens 1502. As will be describedin greater detail herein, the pressure measurement can be used topredict the user's intention for changing the weight of a line, type ofa line, type of brush, click, double click, and the like. Inembodiments, the pressure sensor may be constructed using any force orpressure measurement sensor located behind the lens 1502, including forexample, a resistive sensor, a current sensor, a capacitive sensor, avoltage sensor such as a piezoelectric sensor, and the like.

The pen 1500 may also include a communications module 1518, such as forbi-directional communication with the HWC 102. In embodiments, thecommunications module 1518 may be a short distance communication module(e.g. Bluetooth). The communications module 1518 may be security matchedto the HWC 102. The communications module 1518 may be arranged tocommunicate data and commands to and from the microprocessor 1510 of thepen 1500. The microprocessor 1510 may be programmed to interpret datagenerated from the camera 1508, IMU 1512, and pressure sensor 1504, andthe like, and then pass a command onto the HWC 102 through thecommunications module 1518, for example. In another embodiment, the datacollected from any of the input sources (e.g. camera 1508, IMU 1512,pressure sensor 1504) by the microprocessor may be communicated by thecommunication module 1518 to the HWC 102, and the HWC 102 may performdata processing and prediction of the user's intention when using thepen 1500. In yet another embodiment, the data may be further passed onthrough a network 110 to a remote device 112, such as a server, for thedata processing and prediction. The commands may then be communicatedback to the HWC 102 for execution (e.g. display writing in the glassesdisplay, make a selection within the UI of the glasses display, controla remote external device 112, control a local external device 108), andthe like. The pen may also include memory 1514 for long or short termuses.

The pen 1500 may also include a number of physical user interfaces, suchas quick launch buttons 1522, a touch sensor 1520, and the like. Thequick launch buttons 1522 may be adapted to provide the user with a fastway of jumping to a software application in the HWC system 100. Forexample, the user may be a frequent user of communication softwarepackages (e.g. email, text, Twitter, Instagram, Facebook, Google+, andthe like), and the user may program a quick launch button 1522 tocommand the HWC 102 to launch an application. The pen 1500 may beprovided with several quick launch buttons 1522, which may be userprogrammable or factory programmable. The quick launch button 1522 maybe programmed to perform an operation. For example, one of the buttonsmay be programmed to clear the digital display of the HWC 102. Thiswould create a fast way for the user to clear the screens on the HWC 102for any reason, such as for example to better view the environment. Thequick launch button functionality will be discussed in further detailbelow. The touch sensor 1520 may be used to take gesture style inputfrom the user. For example, the user may be able to take a single fingerand run it across the touch sensor 1520 to affect a page scroll.

The pen 1500 may also include a laser pointer 1524. The laser pointer1524 may be coordinated with the IMU 1512 to coordinate gestures andlaser pointing. For example, a user may use the laser 1524 in apresentation to help with guiding the audience with the interpretationof graphics and the IMU 1512 may, either simultaneously or when thelaser 1524 is off, interpret the user's gestures as commands or datainput.

FIGS. 16A-C illustrate several embodiments of lens and cameraarrangements 1600 for the pen 1500. One aspect relates to maintaining aconstant distance between the camera and the writing surface to enablethe writing surface to be kept in focus for better tracking of movementsof the pen 1500 over the writing surface. Another aspect relates tomaintaining an angled surface following the circumference of the writingtip of the pen 1500 such that the pen 1500 can be rolled or partiallyrolled in the user's hand to create the feel and freedom of aconventional writing instrument.

FIG. 16A illustrates an embodiment of the writing lens end of the pen1500. The configuration includes a ball lens 1604, a camera or imagecapture surface 1602, and a domed cover lens 1608. In this arrangement,the camera views the writing surface through the ball lens 1604 and domecover lens 1608. The ball lens 1604 causes the camera to focus such thatthe camera views the writing surface when the pen 1500 is held in thehand in a natural writing position, such as with the pen 1500 in contactwith a writing surface. In embodiments, the ball lens 1604 should beseparated from the writing surface to obtain the highest resolution ofthe writing surface at the camera 1602. In embodiments, the ball lens1604 is separated by approximately 1 to 3 mm. In this configuration, thedomed cover lens 1608 provides a surface that can keep the ball lens1604 separated from the writing surface at a constant distance, such assubstantially independent of the angle used to write on the writingsurface. For instance, in embodiments the field of view of the camera inthis arrangement would be approximately 60 degrees.

The domed cover lens, or other lens 1608 used to physically interactwith the writing surface, will be transparent or transmissive within theactive bandwidth of the camera 1602. In embodiments, the domed coverlens 1608 may be spherical or other shape and comprised of glass,plastic, sapphire, diamond, and the like. In other embodiments where lowresolution imaging of the surface is acceptable. The pen 1500 can omitthe domed cover lens 1608 and the ball lens 1604 can be in directcontact with the surface.

FIG. 16B illustrates another structure where the construction issomewhat similar to that described in connection with FIG. 16A; howeverthis embodiment does not use a dome cover lens 1608, but instead uses aspacer 1610 to maintain a predictable distance between the ball lens1604 and the writing surface, wherein the spacer may be spherical,cylindrical, tubular or other shape that provides spacing while allowingfor an image to be obtained by the camera 1602 through the lens 1604. Ina preferred embodiment, the spacer 1610 is transparent. In addition,while the spacer 1610 is shown as spherical, other shapes such as anoval, doughnut shape, half sphere, cone, cylinder or other form may beused.

FIG. 16C illustrates yet another embodiment, where the structureincludes a post 1614, such as running through the center of the lensedend of the pen 1500. The post 1614 may be an ink deposition system (e.g.ink cartridge), graphite deposition system (e.g. graphite holder), or adummy post whose purpose is mainly only that of alignment. The selectionof the post type is dependent on the pen's use. For instance, in theevent the user wants to use the pen 1500 as a conventional inkdepositing pen as well as a fully functional external user interface104, the ink system post would be the best selection. If there is noneed for the ‘writing’ to be visible on the writing surface, theselection would be the dummy post. The embodiment of FIG. 16C includescamera(s) 1602 and an associated lens 1612, where the camera 1602 andlens 1612 are positioned to capture the writing surface withoutsubstantial interference from the post 1614. In embodiments, the pen1500 may include multiple cameras 1602 and lenses 1612 such that more orall of the circumference of the tip 1614 can be used as an input system.In an embodiment, the pen 1500 includes a contoured grip that keeps thepen aligned in the user's hand so that the camera 1602 and lens 1612remains pointed at the surface.

Another aspect of the pen 1500 relates to sensing the force applied bythe user to the writing surface with the pen 1500. The force measurementmay be used in a number of ways. For example, the force measurement maybe used as a discrete value, or discontinuous event tracking, andcompared against a threshold in a process to determine a user's intent.The user may want the force interpreted as a ‘click’ in the selection ofan object, for instance. The user may intend multiple force exertionsinterpreted as multiple clicks. There may be times when the user holdsthe pen 1500 in a certain position or holds a certain portion of the pen1500 (e.g. a button or touch pad) while clicking to affect a certainoperation (e.g. a ‘right click’). In embodiments, the force measurementmay be used to track force and force trends. The force trends may betracked and compared to threshold limits, for example. There may be onesuch threshold limit, multiple limits, groups of related limits, and thelike. For example, when the force measurement indicates a fairlyconstant force that generally falls within a range of related thresholdvalues, the microprocessor 1510 may interpret the force trend as anindication that the user desires to maintain the current writing style,writing tip type, line weight, brush type, and the like. In the eventthat the force trend appears to have gone outside of a set of thresholdvalues intentionally, the microprocessor may interpret the action as anindication that the user wants to change the current writing style,writing tip type, line weight, brush type, and the like. Once themicroprocessor has made a determination of the user's intent, a changein the current writing style, writing tip type, line weight, brush type,and the like may be executed. In embodiments, the change may be noted tothe user (e.g. in a display of the HWC 102), and the user may bepresented with an opportunity to accept the change.

FIG. 17A illustrates an embodiment of a force sensing surface tip 1700of a pen 1500. The force sensing surface tip 1700 comprises a surfaceconnection tip 1702 (e.g. a lens as described herein elsewhere) inconnection with a force or pressure monitoring system 1504. As a useruses the pen 1500 to write on a surface or simulate writing on a surfacethe force monitoring system 1504 measures the force or pressure the userapplies to the writing surface and the force monitoring systemcommunicates data to the microprocessor 1510 for processing. In thisconfiguration, the microprocessor 1510 receives force data from theforce monitoring system 1504 and processes the data to make predictionsof the user's intent in applying the particular force that is currentlybeing applied. In embodiments, the processing may be provided at alocation other than on the pen (e.g. at a server in the HWC system 100,on the HWC 102). For clarity, when reference is made herein toprocessing information on the microprocessor 1510, the processing ofinformation contemplates processing the information at a location otherthan on the pen. The microprocessor 1510 may be programmed with forcethreshold(s), force signature(s), force signature library and/or othercharacteristics intended to guide an inference program in determiningthe user's intentions based on the measured force or pressure. Themicroprocessor 1510 may be further programmed to make inferences fromthe force measurements as to whether the user has attempted to initiatea discrete action (e.g. a user interface selection ‘click’) or isperforming a constant action (e.g. writing within a particular writingstyle). The inferencing process is important as it causes the pen 1500to act as an intuitive external user interface 104.

FIG. 17B illustrates a force 1708 versus time 1710 trend chart with asingle threshold 1718. The threshold 1718 may be set at a level thatindicates a discrete force exertion indicative of a user's desire tocause an action (e.g. select an object in a GUI). Event 1712, forexample, may be interpreted as a click or selection command because theforce quickly increased from below the threshold 1718 to above thethreshold 1718. The event 1714 may be interpreted as a double clickbecause the force quickly increased above the threshold 1718, decreasedbelow the threshold 1718 and then essentially repeated quickly. The usermay also cause the force to go above the threshold 1718 and hold for aperiod indicating that the user is intending to select an object in theGUI (e.g. a GUI presented in the display of the HWC 102) and ‘hold’ fora further operation (e.g. moving the object).

While a threshold value may be used to assist in the interpretation ofthe user's intention, a signature force event trend may also be used.The threshold and signature may be used in combination or either methodmay be used alone. For example, a single-click signature may berepresented by a certain force trend signature or set of signatures. Thesingle-click signature(s) may require that the trend meet a criteria ofa rise time between x and y values, a hold time of between a and bvalues and a fall time of between c and d values, for example.Signatures may be stored for a variety of functions such as click,double click, right click, hold, move, etc. The microprocessor 1510 maycompare the real-time force or pressure tracking against the signaturesfrom a signature library to make a decision and issue a command to thesoftware application executing in the GUI.

FIG. 17C illustrates a force 1708 versus time 1710 trend chart withmultiple thresholds 1718. By way of example, the force trend is plottedon the chart with several pen force or pressure events. As noted, thereare both presumably intentional events 1720 and presumablynon-intentional events 1722. The two thresholds 1718 of FIG. 4C createthree zones of force: a lower, middle and higher range. The beginning ofthe trend indicates that the user is placing a lower zone amount offorce. This may mean that the user is writing with a given line weightand does not intend to change the weight, the user is writing. Then thetrend shows a significant increase 1720 in force into the middle forcerange. This force change appears, from the trend to have been sudden andthereafter it is sustained. The microprocessor 1510 may interpret thisas an intentional change and as a result change the operation inaccordance with preset rules (e.g. change line width, increase lineweight, etc.). The trend then continues with a second apparentlyintentional event 1720 into the higher-force range. During theperformance in the higher-force range, the force dips below the upperthreshold 1718. This may indicate an unintentional force change and themicroprocessor may detect the change in range however not affect achange in the operations being coordinated by the pen 1500. As indicatedabove, the trend analysis may be done with thresholds and/or signatures.

Generally, in the present disclosure, instrument stroke parameterchanges may be referred to as a change in line type, line weight, tiptype, brush type, brush width, brush pressure, color, and other forms ofwriting, coloring, painting, and the like.

Another aspect of the pen 1500 relates to selecting an operating modefor the pen 1500 dependent on contextual information and/or selectioninterface(s). The pen 1500 may have several operating modes. Forinstance, the pen 1500 may have a writing mode where the userinterface(s) of the pen 1500 (e.g. the writing surface end, quick launchbuttons 1522, touch sensor 1520, motion based gesture, and the like) isoptimized or selected for tasks associated with writing. As anotherexample, the pen 1500 may have a wand mode where the user interface(s)of the pen is optimized or selected for tasks associated with softwareor device control (e.g. the HWC 102, external local device, remotedevice 112, and the like). The pen 1500, by way of another example, mayhave a presentation mode where the user interface(s) is optimized orselected to assist a user with giving a presentation (e.g. pointing withthe laser pointer 1524 while using the button(s) 1522 and/or gestures tocontrol the presentation or applications relating to the presentation).The pen may, for example, have a mode that is optimized or selected fora particular device that a user is attempting to control. The pen 1500may have a number of other modes and an aspect of the present inventionrelates to selecting such modes.

FIG. 18A illustrates an automatic user interface(s) mode selection basedon contextual information. The microprocessor 1510 may be programmedwith IMU thresholds 1814 and 1812. The thresholds 1814 and 1812 may beused as indications of upper and lower bounds of an angle 1804 and 1802of the pen 1500 for certain expected positions during certain predictedmodes. When the microprocessor 1510 determines that the pen 1500 isbeing held or otherwise positioned within angles 1802 corresponding towriting thresholds 1814, for example, the microprocessor 1510 may theninstitute a writing mode for the pen's user interfaces. Similarly, ifthe microprocessor 1510 determines (e.g. through the IMU 1512) that thepen is being held at an angle 1804 that falls between the predeterminedwand thresholds 1812, the microprocessor may institute a wand mode forthe pen's user interface. Both of these examples may be referred to ascontext based user interface mode selection as the mode selection isbased on contextual information (e.g. position) collected automaticallyand then used through an automatic evaluation process to automaticallyselect the pen's user interface(s) mode.

As with other examples presented herein, the microprocessor 1510 maymonitor the contextual trend (e.g. the angle of the pen over time) in aneffort to decide whether to stay in a mode or change modes. For example,through signatures, thresholds, trend analysis, and the like, themicroprocessor may determine that a change is an unintentional changeand therefore no user interface mode change is desired.

FIG. 18B illustrates an automatic user interface(s) mode selection basedon contextual information. In this example, the pen 1500 is monitoring(e.g. through its microprocessor) whether or not the camera at thewriting surface end 1508 is imaging a writing surface in close proximityto the writing surface end of the pen 1500. If the pen 1500 determinesthat a writing surface is within a predetermined relatively shortdistance, the pen 1500 may decide that a writing surface is present 1820and the pen may go into a writing mode user interface(s) mode. In theevent that the pen 1500 does not detect a relatively close writingsurface 1822, the pen may predict that the pen is not currently beingused to as a writing instrument and the pen may go into a non-writinguser interface(s) mode.

FIG. 18C illustrates a manual user interface(s) mode selection. The userinterface(s) mode may be selected based on a twist of a section 1824 ofthe pen 1500 housing, clicking an end button 1828, pressing a quicklaunch button 1522, interacting with touch sensor 1520, detecting apredetermined action at the pressure monitoring system (e.g. a click),detecting a gesture (e.g. detected by the IMU), etc. The manual modeselection may involve selecting an item in a GUI associated with the pen1500 (e.g. an image presented in the display of HWC 102).

In embodiments, a confirmation selection may be presented to the user inthe event a mode is going to change. The presentation may be physical(e.g. a vibration in the pen 1500), through a GUI, through a lightindicator, etc.

FIG. 19 illustrates a couple pen use-scenarios 1900 and 1901. There aremany use scenarios and we have presented a couple in connection withFIG. 19 as a way of illustrating use scenarios to further theunderstanding of the reader. As such, the use-scenarios should beconsidered illustrative and non-limiting.

Use scenario 1900 is a writing scenario where the pen 1500 is used as awriting instrument. In this example, quick launch button 122A is pressedto launch a note application 1910 in the GUI 1908 of the HWC 102 display1904. Once the quick launch button 122A is pressed, the HWC 102 launchesthe note program 1910 and puts the pen into a writing mode. The useruses the pen 1500 to scribe symbols 1902 on a writing surface, the penrecords the scribing and transmits the scribing to the HWC 102 wheresymbols representing the scribing are displayed 1912 within the noteapplication 1910.

Use scenario 1901 is a gesture scenario where the pen 1500 is used as agesture capture and command device. In this example, the quick launchbutton 122B is activated and the pen 1500 activates a wand mode suchthat an application launched on the HWC 102 can be controlled. Here, theuser sees an application chooser 1918 in the display(s) of the HWC 102where different software applications can be chosen by the user. Theuser gestures (e.g. swipes, spins, turns, etc.) with the pen to causethe application chooser 1918 to move from application to application.Once the correct application is identified (e.g. highlighted) in thechooser 1918, the user may gesture or click or otherwise interact withthe pen 1500 such that the identified application is selected andlaunched. Once an application is launched, the wand mode may be used toscroll, rotate, change applications, select items, initiate processes,and the like, for example.

In an embodiment, the quick launch button 122A may be activated and theHWC 102 may launch an application chooser presenting to the user a setof applications. For example, the quick launch button may launch achooser to show all communication programs (e.g. SMS, Twitter,Instagram, Facebook, email, etc.) available for selection such that theuser can select the program the user wants and then go into a writingmode. By way of further example, the launcher may bring up selectionsfor various other groups that are related or categorized as generallybeing selected at a given time (e.g. Microsoft Office products,communication products, productivity products, note products,organizational products, and the like).

FIG. 20 illustrates yet another embodiment of the present invention.FIG. 20 illustrates a watchband clip on controller 2000. The watchbandclip on controller may be a controller used to control the HWC 102 ordevices in the HWC system 100. The watchband clip on controller 2000 hasa fastener 2018 (e.g. rotatable clip) that is mechanically adapted toattach to a watchband, as illustrated at 2004.

The watchband controller 2000 may have quick launch interfaces 2008(e.g. to launch applications and choosers as described herein), a touchpad 2014 (e.g. to be used as a touch style mouse for GUI control in aHWC 102 display) and a display 2012. The clip 2018 may be adapted to fita wide range of watchbands so it can be used in connection with a watchthat is independently selected for its function. The clip, inembodiments, is rotatable such that a user can position it in adesirable manner. In embodiments the clip may be a flexible strap. Inembodiments, the flexible strap may be adapted to be stretched to attachto a hand, wrist, finger, device, weapon, and the like.

In embodiments, the watchband controller may be configured as aremovable and replaceable watchband. For example, the controller may beincorporated into a band with a certain width, segment spacing's, etc.such that the watchband, with its incorporated controller, can beattached to a watch body. The attachment, in embodiments, may bemechanically adapted to attach with a pin upon which the watchbandrotates. In embodiments, the watchband controller may be electricallyconnected to the watch and/or watch body such that the watch, watch bodyand/or the watchband controller can communicate data between them.

The watchband controller may have 3-axis motion monitoring (e.g. throughan IMU, accelerometers, magnetometers, gyroscopes, etc.) to capture usermotion. The user motion may then be interpreted for gesture control.

In embodiments, the watchband controller may comprise fitness sensorsand a fitness computer. The sensors may track heart rate, caloriesburned, strides, distance covered, and the like. The data may then becompared against performance goals and/or standards for user feedback.

Another aspect of the present invention relates to visual displaytechniques relating to micro Doppler (“mD”) target tracking signatures(“mD signatures”). mD is a radar technique that uses a series of angledependent electromagnetic pulses that are broadcast into an environmentand return pulses are captured. Changes between the broadcast pulse andreturn pulse are indicative of changes in the shape, distance andangular location of objects or targets in the environment. These changesprovide signals that can be used to track a target and identify thetarget through the mD signature. Each target or target type has a uniquemD signature. Shifts in the radar pattern can be analyzed in the timedomain and frequency domain based on mD techniques to derive informationabout the types of targets present (e.g. whether people are present),the motion of the targets and the relative angular location of thetargets and the distance to the targets. By selecting a frequency usedfor the mD pulse relative to known objects in the environment, the pulsecan penetrate the known objects to enable information about targets tobe gathered even when the targets are visually blocked by the knownobjects. For example, pulse frequencies can be used that will penetrateconcrete buildings to enable people to be identified inside thebuilding. Multiple pulse frequencies can be used as well in the mD radarto enable different types of information to be gathered about theobjects in the environment. In addition, the mD radar information can becombined with other information such as distance measurements or imagescaptured of the environment that are analyzed jointly to provideimproved object identification and improved target identification andtracking. In embodiments, the analysis can be performed on the HWC orthe information can be transmitted to a remote network for analysis andresults transmitted back to the HWC. Distance measurements can beprovided by laser range finding, structured lighting, stereoscopic depthmaps or sonar measurements. Images of the environment can be capturedusing one or more cameras capable of capturing images from visible,ultraviolet or infrared light. The mD radar can be attached to the HWC,located adjacently (e.g. in a vehicle) and associated wirelessly withthe HWC or located remotely. Maps or other previously determinedinformation about the environment can also be used in the analysis ofthe mD radar information. Embodiments of the present invention relate tovisualizing the mD signatures in useful ways.

FIG. 21 illustrates a FOV 2102 of a HWC 102 from a wearer's perspective.The wearer, as described herein elsewhere, has a see-through FOV 2102wherein the wearer views adjacent surroundings, such as the buildingsillustrated in FIG. 21. The wearer, as described herein elsewhere, canalso see displayed digital content presented within a portion of the FOV2102. The embodiment illustrated in FIG. 21 is indicating that thewearer can see the buildings and other surrounding elements in theenvironment and digital content representing traces, or travel paths, ofbullets being fired by different people in the area. The surroundingsare viewed through the transparency of the FOV 2102. The traces arepresented via the digital computer display, as described hereinelsewhere. In embodiments, the trace presented is based on a mDsignature that is collected and communicated to the HWC in real time.The mD radar itself may be on or near the wearer of the HWC 102 or itmay be located remote from the wearer. In embodiments, the mD radarscans the area, tracks and identifies targets, such as bullets, andcommunicates traces, based on locations, to the HWC 102.

There are several traces 2108 and 2104 presented to the wearer in theembodiment illustrated in FIG. 21. The traces communicated from the mDradar may be associated with GPS locations and the GPS locations may beassociated with objects in the environment, such as people, buildings,vehicles, etc, both in latitude and longitude perspective and anelevation perspective. The locations may be used as markers for the HWCsuch that the traces, as presented in the FOV, can be associated, orfixed in space relative to the markers. For example, if the friendlyfire trace 2108 is determined, by the mD radar, to have originated fromthe upper right window of the building on the left, as illustrated inFIG. 21, then a virtual marker may be set on or near the window. Whenthe HWC views, through its camera or other sensor, for example, thebuilding's window, the trace may then virtually anchor with the virtualmarker on the window. Similarly, a marker may be set near thetermination position or other flight position of the friendly fire trace2108, such as the upper left window of the center building on the right,as illustrated in FIG. 21. This technique fixes in space the trace suchthat the trace appears fixed to the environmental positions independentof where the wearer is looking. So, for example, as the wearer's headturns, the trace appears fixed to the marked locations.

In embodiments, certain user positions may be known and thus identifiedin the FOV. For example, the shooter of the friendly fire trace 2108 maybe from a known friendly combatant and as such his location may beknown. The position may be known based on his GPS location based on amobile communication system on him, such as another HWC 102. In otherembodiments, the friendly combatant may be marked by another friendly.For example, if the friendly position in the environment is knownthrough visual contact or communicated information, a wearer of the HWC102 may use a gesture or external user interface 104 to mark thelocation. if a friendly combatant location is known the originatingposition of the friendly fire trace 2108 may be color coded or otherwisedistinguished from unidentified traces on the displayed digital content.Similarly, enemy fire traces 2104 may be color coded or otherwisedistinguished on the displayed digital content. In embodiments, theremay be an additional distinguished appearance on the displayed digitalcontent for unknown traces.

In addition to situationally associated trace appearance, the tracecolors or appearance may be different from the originating position tothe terminating position. This path appearance change may be based onthe mD signature. The mD signature may indicate that the bullet, forexample, is slowing as it propagates and this slowing pattern may bereflected in the FOV 2102 as a color or pattern change. This can createan intuitive understanding of wear the shooter is located. For example,the originating color may be red, indicative of high speed, and it maychange over the course of the trace to yellow, indicative of a slowingtrace. This pattern changing may also be different for a friendly, enemyand unknown combatant. The enemy may go blue to green for a friendlytrace, for example.

FIG. 21 illustrates an embodiment where the user sees the environmentthrough the FOV and may also see color coded traces, which are dependenton bullet speed and combatant type, where the traces are fixed inenvironmental positions independent on the wearer's perspective. Otherinformation, such as distance, range, range rings, time of day, date,engagement type (e.g. hold, stop firing, back away, etc.) may also bedisplayed in the FOV.

Another aspect of the present invention relates to mD radar techniquesthat trace and identify targets through other objects, such as walls(referred to generally as through wall mD), and visualization techniquesrelated therewith. FIG. 22 illustrates a through wall mD visualizationtechnique according to the principles of the present invention. Asdescribed herein elsewhere, the mD radar scanning the environment may belocal or remote from the wearer of a HWC 102. The mD radar may identifya target (e.g. a person) that is visible 2204 and then track the targetas he goes behind a wall 2208. The tracking may then be presented to thewearer of a HWC 102 such that digital content reflective of the targetand the target's movement, even behind the wall, is presented in the FOV2202 of the HWC 102. In embodiments, the target, when out of visiblesight, may be represented by an avatar in the FOV to provide the wearerwith imagery representing the target.

mD target recognition methods can identify the identity of a targetbased on the vibrations and other small movements of the target. Thiscan provide a personal signature for the target. In the case of humans,this may result in a personal identification of a target that has beenpreviously characterized. The cardio, heartbeat, lung expansion andother small movements within the body may be unique to a person and ifthose attributes are pre-identified they may be matched in real time toprovide a personal identification of a person in the FOV 2202. Theperson's mD signatures may be determined based on the position of theperson. For example, the database of personal mD signature attributesmay include mD signatures for a person standing, sitting, laying down,running, walking, jumping, etc. This may improve the accuracy of thepersonal data match when a target is tracked through mD signaturetechniques in the field. In the event a person is personally identified,a specific indication of the person's identity may be presented in theFOV 2202. The indication may be a color, shape, shade, name, indicationof the type of person (e.g. enemy, friendly, etc.), etc. to provide thewearer with intuitive real time information about the person beingtracked. This may be very useful in a situation where there is more thanone person in an area of the person being tracked. If just one person inthe area is personally identified, that person or the avatar of thatperson can be presented differently than other people in the area.

FIG. 23 illustrates an mD scanned environment 2300. An mD radar may scanan environment in an attempt to identify objects in the environment. Inthis embodiment, the mD scanned environment reveals two vehicles 2302 aand 2302 b, an enemy combatant 2309, two friendly combatants 2308 a and2308 b and a shot trace 2318. Each of these objects may be personallyidentified or type identified. For example, the vehicles 2302 a and 2302b may be identified through the mD signatures as a tank and heavy truck.The enemy combatant 2309 may be identified as a type (e.g. enemycombatant) or more personally (e.g. by name). The friendly combatantsmay be identified as a type (e.g. friendly combatant) or more personally(e.g. by name). The shot trace 2318 may be characterized by type ofprojectile or weapon type for the projectile, for example.

FIG. 23a illustrates two separate HWC 102 FOV display techniquesaccording to the principles of the present invention. FOV 2312illustrates a map view 2310 where the mD scanned environment ispresented. Here, the wearer has a perspective on the mapped area so hecan understand all tracked targets in the area. This allows the wearerto traverse the area with knowledge of the targets. FOV 2312 illustratesa heads-up view to provide the wearer with an augmented reality styleview of the environment that is in proximity of the wearer.

An aspect of the present invention relates to suppression of extraneousor stray light. As discussed herein elsewhere, eyeglow and faceglow aretwo such artifacts that develop from such light. Eyeglow and faceglowcan be caused by image light escaping from the optics module. Theescaping light is then visible, particularly in dark environments whenthe user is viewing bright displayed images with the HWC. Light thatescapes through the front of the HWC is visible as eyeglow as it thatlight that is visible in the region of the user's eyes. Eyeglow canappear in the form of a small version of the displayed image that theuser is viewing. Light that escapes from the bottom of the HWC shinesonto the user's face, cheek or chest so that these portions of the userappear to glow. Eyeglow and faceglow can both increase the visibility ofthe user and highlight the use of the HWC, which may be viewednegatively by the user. As such, reducing eyeglow and faceglow isadvantageous. In combat situations (e.g. the mD trace presentationscenarios described herein) and certain gaming situations, thesuppression of extraneous or stray light is very important.

The disclosure relating to FIG. 6 shows an example where a portion ofthe image light passes through the combiner 602 such that the lightshines onto the user's face, thereby illuminating a portion of theuser's face in what is generally referred to herein as faceglow.Faceglow be caused by any portion of light from the HWC that illuminatesthe user's face.

An example of the source for the faceglow light can come from wide coneangle light associated with the image light incident onto the combiner602. Where the combiner can include a holographic mirror or a notchmirror in which the narrow bands of high reflectivity are matched towavelengths of light by the light source. The wide cone angle associatedwith the image light corresponds with the field of view provided by theHWC. Typically the reflectivity of holographic mirrors and notch mirrorsis reduced as the cone angle of the incident light is increased above 8degrees. As a result, for a field of view of 30 degrees, substantialimage light can pass through the combiner and cause faceglow.

FIG. 24 shows an illustration of a light trap 2410 for the faceglowlight. In this embodiment, an extension of the outer shield lens of theHWC is coated with a light absorbing material in the region where theconverging light responsible for faceglow is absorbed in a light trap2410. The light absorbing material can be black or it can be a filterdesigned to absorb only the specific wavelengths of light provided bythe light source(s) in the HWC. In addition, the surface of the lighttrap 2410 may be textured or fibrous to further improve the absorption.

FIG. 25 illustrates an optical system for a HWC that includes an outerabsorptive polarizer 2520 to block the faceglow light. In thisembodiment, the image light is polarized and as a result the lightresponsible for faceglow is similarly polarized. The absorptivepolarizer is oriented with a transmission axis such that the faceglowlight is absorbed and not transmitted. In this case, the rest of theimaging system in the HWC may not require polarized image light and theimage light may be polarized at any point before the combiner. Inembodiments, the transmission axis of the absorptive polarizer 2520 isoriented vertically so that external glare from water (S polarizedlight) is absorbed and correspondingly, the polarization of the imagelight is selected to be horizontal (S polarization). Consequently, imagelight that passes through the combiner 602 and is then incident onto theabsorptive polarizer 2520, is absorbed. In FIG. 25 the absorptivepolarizer 2520 is shown outside the shield lens, alternatively theabsorptive polarizer 2520 can be located inside the shield lens.

FIG. 26 illustrates an optical system for a HWC that includes a filmwith an absorptive notch filter 2620. In this case, the absorptive notchfilter absorbs narrow bands of light that are selected to match thelight provided by the optical system's light source. As a result, theabsorptive notch filter is opaque with respect to the faceglow light andis transparent to the remainder of the wavelengths included in thevisible spectrum so that the user has a clear view of the surroundingenvironment. A triple notch filter suitable for this approach isavailable from Iridian Spectral Technologies, Ottawa, ON:http://www.ilphotonics.com/cdv2/Iridian-Interference %20Filters/New%20filters/Triple %20Notch %20Filter.pdf

In embodiments, the combiner 602 may include a notch mirror coating toreflect the wavelengths of light in the image light and a notch filter2620 can be selected in correspondence to the wavelengths of lightprovided by the light source and the narrow bands of high reflectivityprovided by the notch mirror. In this way, image light that is notreflected by the notch mirror is absorbed by the notch filter 2620. Inembodiments of the invention the light source can provide one narrowband of light for a monochrome imaging or three narrow bands of lightfor full color imaging. The notch mirror and associated notch filterwould then each provide one narrow band or three narrow bands of highreflectivity and absorption respectively.

FIG. 27 includes a microlouver film 2750 to block the faceglow light.Microlouver film is sold by 3M as ALCF-P, for example, and is typicallyused as a privacy filter for computer. See http://multimedia.3m.com/mws/mediawebserver?mwsld=SSSSSuH8gc7nZx+UoY_xlY_eevUqe17zHvTSevTSeSSSSSS--&fn=ALCF-P_ABR2_Control_Film_DS.pdf.The microlouver film transmits light within a somewhat narrow angle(e.g. 30 degrees of normal and absorbs light beyond 30 degrees ofnormal). In FIG. 27, the microlouver film 2750 is positioned such thatthe faceglow light 2758 is incident beyond 30 degrees from normal whilethe see-through light 2755 is incident within 30 degrees of normal tothe microlouver film 2750. As such, the faceglow light 2758 is absorbedby the microlouver film and the see-through light 2755 is transmitted sothat the user has a bright see-thru view of the surrounding environment.

We now turn back to a description of eye imaging technologies. Aspectsof the present invention relate to various methods of imaging the eye ofa person wearing the HWC 102. In embodiments, technologies for imagingthe eye using an optical path involving the “off” state and “no power”state, which is described in detail below, are described. Inembodiments, technologies for imaging the eye with opticalconfigurations that do not involve reflecting the eye image off of DLPmirrors is described. In embodiments, unstructured light, structuredlight, or controlled lighting conditions, are used to predict the eye'sposition based on the light reflected off of the front of the wearer'seye. In embodiments, a reflection of a presented digital content imageis captured as it reflects off of the wearer's eye and the reflectedimage may be processed to determine the quality (e.g. sharpness) of theimage presented. In embodiments, the image may then be adjusted (e.g.focused differently) to increase the quality of the image presentedbased on the image reflection.

FIGS. 28a, 28b and 28c show illustrations of the various positions ofthe DLP mirrors. FIG. 28a shows the DLP mirrors in the “on” state 2815.With the mirror in the “on” state 2815, illumination light 2810 isreflected along an optical axis 2820 that extends into the lower opticalmodule 204. FIG. 28b shows the DLP mirrors in the “off” state 2825. Withthe mirror in the “off” state 2825, illumination light 2810 is reflectedalong an optical axis 2830 that is substantially to the side of opticalaxis 2820 so that the “off” state light is directed toward a dark lighttrap as has been described herein elsewhere. FIG. 28c shows the DLPmirrors in a third position, which occurs when no power is applied tothe DLP. This “no power” state differs from the “on” and “off” states inthat the mirror edges are not in contact with the substrate and as suchare less accurately positioned. FIG. 28c shows all of the DLP mirrors inthe “no power” state 2835. The “no power” state is achieved bysimultaneously setting the voltage to zero for the “on” contact and“off” contact for a DLP mirror, as a result, the mirror returns to a nostress position where the DLP mirror is in the plane of the DLP platformas shown in FIG. 28c . Although not normally done, it is also possibleto apply the “no power” state to individual DLP mirrors. When the DLPmirrors are in the “no power” state they do not contribute imagecontent. Instead, as shown in FIG. 28c , when the DLP mirrors are in the“no power” state, the illumination light 2810 is reflected along anoptical axis 2840 that is between the optical axes 2820 and 2830 thatare respectively associated with the “on” and “off” states and as suchthis light doesn't contribute to the displayed image as a bright or darkpixel. This light can however contribute scattered light into the loweroptical module 204 and as a result the displayed image contrast can bereduced or artifacts can be created in the image that detract from theimage content. Consequently, it is generally desirable, in embodiments,to limit the time associated with the “no power” state to times whenimages are not displayed or to reduce the time associated with havingDLP mirrors in the “no power” state so that the effect of the scatteredlight is reduced.

FIG. 29 shows an embodiment of the invention that can be used fordisplaying digital content images to a wearer of the HWC 102 andcapturing images of the wearer's eye. In this embodiment, light from theeye 2971 passes back through the optics in the lower module 204, thesolid corrective wedge 2966, at least a portion of the light passesthrough the partially reflective layer 2960, the solid illuminationwedge 2964 and is reflected by a plurality of DLP mirrors on the DLP2955 that are in the “no power” state. The reflected light then passesback through the illumination wedge 2964 and at least a portion of thelight is reflected by the partially reflective layer 2960 and the lightis captured by the camera 2980.

For comparison, illuminating light rays 2973 from the light source 2958are also shown being reflected by the partially reflective layer 2960.Where the angle of the illuminating light 2973 is such that the DLPmirrors, when in the “on” state, reflect the illuminating light 2973 toform image light 2969 that substantially shares the same optical axis asthe light from the wearer's eye 2971. In this way, images of thewearer's eye are captured in a field of view that overlaps the field ofview for the displayed image content. In contrast, light reflected byDLP mirrors in the “off” state form dark light 2975 which is directedsubstantially to the side of the image light 2969 and the light from eye2971. Dark light 2975 is directed toward a light trap 2962 that absorbsthe dark light to improve the contrast of the displayed image as hasbeen described above in this specification.

In an embodiment, partially reflective layer 2960 is a reflectivepolarizer. The light that is reflected from the eye 2971 can then bepolarized prior to entering the corrective wedge 2966 (e.g. with anabsorptive polarizer between the upper module 202 and the lower module204), with a polarization orientation relative to the reflectivepolarizer that enables the light reflected from the eye 2971 tosubstantially be transmitted by the reflective polarizer. A quarter waveretarder layer 2957 is then included adjacent to the DLP 2955 (aspreviously disclosed in FIG. 3b ) so that the light reflected from theeye 2971 passes through the quarter wave retarder layer 2957 once beforebeing reflected by the plurality of DLP mirrors in the “no power” stateand then passes through a second time after being reflected. By passingthrough the quarter wave retarder layer 2957 twice, the polarizationstate of the light from the eye 2971 is reversed, such that when it isincident upon the reflective polarizer, the light from the eye 2971 isthen substantially reflected toward the camera 2980. By using apartially reflective layer 2960 that is a reflective polarizer andpolarizing the light from the eye 2971 prior to entering the correctivewedge 2964, losses attributed to the partially reflective layer 2960 arereduced.

FIG. 28c shows the case wherein the DLP mirrors are simultaneously inthe “no power” state, this mode of operation can be particularly usefulwhen the HWC 102 is first put onto the head of the wearer. When the HWC102 is first put onto the head of the wearer, it is not necessary todisplay an image yet. As a result, the DLP can be in a “no power” statefor all the DLP mirrors and an image of the wearer's eyes can becaptured. The captured image of the wearer's eye can then be compared toa database, using iris identification techniques, or other eye patternidentification techniques to determine, for example, the identity of thewearer.

In a further embodiment illustrated by FIG. 29 all of the DLP mirrorsare put into the “no power” state for a portion of a frame time (e.g.50% of a frame time for the displayed digital content image) and thecapture of the eye image is synchronized to occur at the same time andfor the same duration. By reducing the time that the DLP mirrors are inthe “no power” state, the time where light is scattered by the DLPmirrors being in the “no power” state is reduced such that the wearerdoesn't perceive a change in the displayed image quality. This ispossible because the DLP mirrors have a response time on the order ofmicroseconds while typical frame times for a displayed image are on theorder of 0.016 seconds. This method of capturing images of the wearer'seye can be used periodically to capture repetitive images of thewearer's eye. For example, eye images could be captured for 50% of theframe time of every 10^(th) frame displayed to the wearer. In anotherexample, eye images could be captured for 10% of the frame time of everyframe displayed to the wearer.

Alternately, the “no power” state can be applied to a subset of the DLPmirrors (e.g. 10% of the DLP mirrors) within while another subset is inbusy generating image light for content to be displayed. This enablesthe capture of an eye image(s) during the display of digital content tothe wearer. The DLP mirrors used for eye imaging can, for example, bedistributed randomly across the area of the DLP to minimize the impacton the quality of the digital content being displayed to the wearer. Toimprove the displayed image perceived by the wearer, the individual DLPmirrors put into the “no power” state for capturing each eye image, canbe varied over time such as in a random pattern, for example. In yet afurther embodiment, the DLP mirrors put into the “no power” state foreye imaging may be coordinated with the digital content in such a waythat the “no power” mirrors are taken from a portion of the image thatrequires less resolution.

In the embodiments of the invention as illustrated in FIGS. 9 and 29, inboth cases the reflective surfaces provided by the DLP mirrors do notpreserve the wavefront of the light from the wearer's eye so that theimage quality of captured image of the eye is somewhat limited. It maystill be useful in certain embodiments, but it is somewhat limited. Thisis due to the DLP mirrors not being constrained to be on the same plane.In the embodiment illustrated in FIG. 9, the DLP mirrors are tilted sothat they form rows of DLP mirrors that share common planes. In theembodiment illustrated in FIG. 29, the individual DLP mirrors are notaccurately positioned to be in the same plane since they are not incontact with the substrate. Examples of advantages of the embodimentsassociated with FIG. 29 are: first, the camera 2980 can be locatedbetween the DLP 2955 and the illumination light source 2958 to provide amore compact upper module 202. Second, the polarization state of thelight reflected from the eye 2971 can be the same as that of the imagelight 2969 so that the optical path of the light reflected from the eyeand the image light can be the same in the lower module 204.

FIG. 30 shows an illustration of an embodiment for displaying images tothe wearer and simultaneously capturing images of the wearer's eye,wherein light from the eye 2971 is reflected towards a camera 3080 bythe partially reflective layer 2960. The partially reflective layer 2960can be an optically flat layer such that the wavefront of the light fromthe eye 2971 is preserved and as a result, higher quality images of thewearer's eye can be captured. In addition, since the DLP 2955 is notincluded in the optical path for the light from the eye 2971, and theeye imaging process shown in FIG. 30 does not interfere with thedisplayed image, images of the wearer's eye can be capturedindependently (e.g. with independent of timing, impact on resolution, orpixel count used in the image light) from the displayed images.

In the embodiment illustrated in FIG. 30, the partially reflective layer2960 is a reflective polarizer, the illuminating light 2973 ispolarized, the light from the eye 2971 is polarized and the camera 3080is located behind a polarizer 3085. The polarization axis of theilluminating light 2973 and the polarization axis of the light from theeye are oriented perpendicular to the transmission axis of thereflective polarizer so that they are both substantially reflected bythe reflective polarizer. The illumination light 2973 passes through aquarter wave layer 2957 before being reflected by the DLP mirrors in theDLP 2955. The reflected light passes back through the quarter wave layer2957 so that the polarization states of the image light 2969 and darklight 2975 are reversed in comparison to the illumination light 2973. Assuch, the image light 2969 and dark light 2975 are substantiallytransmitted by the reflective polarizer. Where the DLP mirrors in the“on” state provide the image light 2969 along an optical axis thatextends into the lower optical module 204 to display an image to thewearer. At the same time, DLP mirrors in the “off” state provide thedark light 2975 along an optical axis that extends to the side of theupper optics module 202. In the region of the corrective wedge 2966where the dark light 2975 is incident on the side of the upper opticsmodule 202, an absorptive polarizer 3085 is positioned with itstransmission axis perpendicular to the polarization axis of the darklight and parallel to the polarization axis of the light from the eye sothat the dark light 2975 is absorbed and the light from the eye 2971 istransmitted to the camera 3080.

FIG. 31 shows an illustration of another embodiment of a system fordisplaying images and simultaneously capturing image of the wearer's eyethat is similar to the one shown in FIG. 30. The difference in thesystem shown in FIG. 31 is that the light from the eye 2971 is subjectedto multiple reflections before being captured by the camera 3180. Toenable the multiple reflections, a mirror 3187 is provided behind theabsorptive polarizer 3185. Therefore, the light from the eye 2971 ispolarized prior to entering the corrective wedge 2966 with apolarization axis that is perpendicular to the transmission axis of thereflective polarizer that comprises the partially reflective layer 2960.In this way, the light from the eye 2971 is reflected first by thereflective polarizer, reflected second by the mirror 3187 and reflectedthird by the reflective polarizer before being captured by the camera3180. While the light from the eye 2971 passes through the absorptivepolarizer 3185 twice, since the polarization axis of the light from theeye 2971 is oriented parallel to the polarization axis of the light fromthe eye 2971, it is substantially transmitted by the absorptivepolarizer 3185. As with the system described in connection with FIG. 30,the system shown in FIG. 31 includes an optically flat partiallyreflective layer 2960 that preserves the wavefront of the light from theeye 2971 so that higher quality images of the wearer's eye can becaptured. Also, since the DLP 2955 is not included in the optical pathfor the light reflected from the eye 2971 and the eye imaging processshown in FIG. 31 does not interfere with the displayed image, images ofthe wearer's eye can be captured independently from the displayedimages.

FIG. 32 shows an illustration of a system for displaying images andsimultaneously capturing images of the wearer's eye that includes a beamsplitter plate 3212 comprised of a reflective polarizer, which is heldin air between the light source 2958, the DLP 2955 and the camera 3280.The illumination light 2973 and the light from the eye 2971 are bothpolarized with polarization axes that are perpendicular to thetransmission axis of the reflective polarizer. As a result, both theillumination light 2973 and the light from the eye 2971 aresubstantially reflected by the reflective polarizer. The illuminationlight 2873 is reflected toward the DLP 2955 by the reflective polarizerand split into image light 2969 and dark light 3275 depending on whetherthe individual DLP mirrors are respectively in the “on” state or the“off” state. By passing through the quarter wave layer 2957 twice, thepolarization state of the illumination light 2973 is reversed incomparison to the polarization state of the image light 2969 and thedark light 3275. As a result, the image light 2969 and the dark light3275 are then substantially transmitted by the reflective polarizer. Theabsorptive polarizer 3285 at the side of the beam splitter plate 3212has a transmission axis that is perpendicular to the polarization axisof the dark light 3275 and parallel to the polarization axis of thelight from the eye 2971 so that the dark light 3275 is absorbed and thelight from the eye 2971 is transmitted to the camera 3280. As in thesystem shown in FIG. 30, the system shown in FIG. 31 includes anoptically flat beam splitter plate 3212 that preserves the wavefront ofthe light from the eye 2971 so that higher quality images of thewearer's eye can be captured. Also, since the DLP 2955 is not includedin the optical path for the light from the eye 2971 and the eye imagingprocess shown in FIG. 31 does not interfere with the displayed image,images of the wearer's eye can be captured independently from thedisplayed images.

Eye imaging systems where the polarization state of the light from theeye 2971 needs to be opposite to that of the image light 2969 (as shownin FIGS. 30, 31 and 32), need to be used with lower modules 204 thatinclude combiners that will reflect both polarization states. As such,these upper modules 202 are best suited for use with the lower modules204 that include combiners that are reflective regardless ofpolarization state, examples of these lower modules are shown in FIGS.6, 8 a, 8 b, 8 c and 24-27.

In a further embodiment shown in FIG. 33, the partially reflective layer3360 is comprised of a reflective polarizer on the side facing theillumination light 2973 and a short pass dichroic mirror on the sidefacing the light from the eye 3371 and the camera 3080. Where the shortpass dichroic mirror is a dielectric mirror coating that transmitsvisible light and reflects infrared light. The partially reflectivelayer 3360 can be comprised of a reflective polarizer bonded to theinner surface of the illumination wedge 2964 and a short pass dielectricmirror coating on the opposing inner surface of the corrective wedge2966, wherein the illumination wedge 2964 and the corrective wedge 2966are then optically bonded together. Alternatively, the partiallyreflective layer 3360 can be comprised of a thin substrate that has areflective polarizer bonded to one side and a short pass dichroic mirrorcoating on the other side, where the partially reflective layer 3360 isthen bonded between the illumination wedge 2964 and the corrective wedge2966. In this embodiment, an infrared light is included to illuminatethe eye so that the light from the eye and the images captured of theeye are substantially comprised of infrared light. The wavelength of theinfrared light is then matched to the reflecting wavelength of theshortpass dichroic mirror and the wavelength that the camera can captureimages, for example an 800 nm wavelength can be used. In this way, theshort pass dichroic mirror transmits the image light and reflects thelight from the eye. The camera 3080 is then positioned at the side ofthe corrective wedge 2966 in the area of the absorbing light trap 3382,which is provided to absorb the dark light 2975. By positioning thecamera 3080 in a depression in the absorbing light trap 3382, scatteringof the dark light 2975 by the camera 3080 can be reduced so that highercontrast images can be displayed to the wearer. An advantage of thisembodiment is that the light from the eye need not be polarized, whichcan simplify the optical system and increase efficiency for the eyeimaging system.

In yet another embodiment shown in FIG. 32a a beam splitter plate 3222is comprised of a reflective polarizer on the side facing theillumination light 2973 and a short pass dichroic mirror on the sidefacing the light from the eye 3271 and the camera 3280. An absorbingsurface 3295 is provided to trap the dark light 3275 and the camera 3280is positioned in an opening in the absorbing surface 3295. In this waythe system of FIG. 32 can be made to function with unpolarized lightfrom the eye 3271.

In embodiments directed to capturing images of the wearer's eye, lightto illuminate the wearer's eye can be provided by several differentsources including: light from the displayed image (i.e. image light);light from the environment that passes through the combiner or otheroptics; light provided by a dedicated eye light, etc. FIGS. 34 and 34 ashow illustrations of dedicated eye illumination lights 3420. FIG. 34shows an illustration from a side view in which the dedicatedillumination eye light 3420 is positioned at a corner of the combiner3410 so that it doesn't interfere with the image light 3415. Thededicated eye illumination light 3420 is pointed so that the eyeillumination light 3425 illuminates the eyebox 3427 where the eye 3430is located when the wearer is viewing displayed images provided by theimage light 3415. FIG. 34a shows an illustration from the perspective ofthe eye of the wearer to show how the dedicated eye illumination light3420 is positioned at the corner of the combiner 3410. While thededicated eye illumination light 3420 is shown at the upper left cornerof the combiner 3410, other positions along one of the edges of thecombiner 3410, or other optical or mechanical components, are possibleas well. In other embodiments, more than one dedicated eye light 3420with different positions can be used. In an embodiment, the dedicatedeye light 3420 is an infrared light that is not visible by the wearer(e.g. 800 nm) so that the eye illumination light 3425 doesn't interferewith the displayed image perceived by the wearer.

FIG. 35 shows a series of illustrations of captured eye images that showthe eye glint (i.e. light that reflects off the front of the eye)produced by a dedicated eye light. In this embodiment of the invention,captured images of the wearer's eye are analyzed to determine therelative positions of the iris 3550, pupil, or other portion of the eye,and the eye glint 3560. The eye glint is a reflected image of thededicated eye light 3420 when the dedicated light is used. FIG. 35illustrates the relative positions of the iris 3550 and the eye glint3560 for a variety of eye positions. By providing a dedicated eye light3420 in a fixed position, combined with the fact that the human eye isessentially spherical, or at least a reliably repeatable shape, the eyeglint provides a fixed reference point against which the determinedposition of the iris can be compared to determine where the wearer islooking, either within the displayed image or within the see-throughview of the surrounding environment. By positioning the dedicated eyelight 3420 at a corner of the combiner 3410, the eye glint 3560 isformed away from the iris 3550 in the captured images. As a result, thepositions of the iris and the eye glint can be determined more easilyand more accurately during the analysis of the captured images, sincethey do not interfere with one another. In a further embodiment, thecombiner includes an associated cut filter that prevents infrared lightfrom the environment from entering the HWC and the camera is an infraredcamera, so that the eye glint is only provided by light from thededicated eye light. For example, the combiner can include a low passfilter that passes visible light while absorbing infrared light and thecamera can include a high pass filter that absorbs visible light whilepassing infrared light.

In an embodiment of the eye imaging system, the lens for the camera isdesigned to take into account the optics associated with the uppermodule 202 and the lower module 204. This is accomplished by designingthe camera to include the optics in the upper module 202 and optics inthe lower module 204, so that a high MTF image is produced, at the imagesensor in the camera, of the wearer's eye. In yet a further embodiment,the camera lens is provided with a large depth of field to eliminate theneed for focusing the camera to enable sharp image of the eye to becaptured. Where a large depth of field is typically provided by a highf/# lens (e.g. f/# >5). In this case, the reduced light gatheringassociated with high f/# lenses is compensated by the inclusion of adedicated eye light to enable a bright image of the eye to be captured.Further, the brightness of the dedicated eye light can be modulated andsynchronized with the capture of eye images so that the dedicated eyelight has a reduced duty cycle and the brightness of infrared light onthe wearer's eye is reduced.

In a further embodiment, FIG. 36a shows an illustration of an eye imagethat is used to identify the wearer of the HWC. In this case, an imageof the wearer's eye 3611 is captured and analyzed for patterns ofidentifiable features 3612. The patterns are then compared to a databaseof eye images to determine the identity of the wearer. After theidentity of the wearer has been verified, the operating mode of the HWCand the types of images, applications, and information to be displayedcan be adjusted and controlled in correspondence to the determinedidentity of the wearer. Examples of adjustments to the operating modedepending on who the wearer is determined to be or not be include:making different operating modes or feature sets available, shuttingdown or sending a message to an external network, allowing guestfeatures and applications to run, etc.

In an illustration of another embodiment using eye imaging, in which thesharpness of the displayed image is determined based on the eye glintproduced by the reflection of the displayed image from the wearer's eyesurface. By capturing images of the wearer's eye 3611, an eye glint3622, which is a small version of the displayed image can be capturedand analyzed for sharpness. If the displayed image is determined to notbe sharp, then an automated adjustment to the focus of the HWC opticscan be performed to improve the sharpness. This ability to perform ameasurement of the sharpness of a displayed image at the surface of thewearer's eye can provide a very accurate measurement of image quality.Having the ability to measure and automatically adjust the focus ofdisplayed images can be very useful in augmented reality imaging wherethe focus distance of the displayed image can be varied in response tochanges in the environment or changes in the method of use by thewearer.

An aspect of the present invention relates to controlling the HWC 102through interpretations of eye imagery. In embodiments, eye-imagingtechnologies, such as those described herein, are used to capture an eyeimage or series of eye images for processing. The image(s) may beprocess to determine a user intended action, an HWC predeterminedreaction, or other action. For example, the imagery may be interpretedas an affirmative user control action for an application on the HWC 102.Or, the imagery may cause, for example, the HWC 102 to react in apre-determined way such that the HWC 102 is operating safely,intuitively, etc.

FIG. 37 illustrates a eye imagery process that involves imaging the HWC102 wearer's eye(s) and processing the images (e.g. through eye imagingtechnologies described herein) to determine in what position 3702 theeye is relative to its neutral or forward looking position and/or theFOV 3708. The process may involve a calibration step where the user isinstructed, through guidance provided in the FOV of the HWC 102, to lookin certain directions such that a more accurate prediction of the eyeposition relative to areas of the FOV can be made. In the event thewearer's eye is determined to be looking towards the right side of theFOV 3708 (as illustrated in FIG. 37, the eye is looking out of thepage), a virtual target line may be established to project what in theenvironment the wearer may be looking towards or at. The virtual targetline may be used in connection with an image captured by camera on theHWC 102 that images the surrounding environment in front of the wearer.In embodiments, the field of view of the camera capturing thesurrounding environment matches, or can be matched (e.g. digitally), tothe FOV 3708 such that making the comparison is made more clear. Forexample, with the camera capturing the image of the surroundings in anangle that matches the FOV 3708 the virtual line can be processed (e.g.in 2d or 3d, depending on the camera images capabilities and/or theprocessing of the images) by projecting what surrounding environmentobjects align with the virtual target line. In the event there aremultiple objects along the virtual target line, focal planes may beestablished corresponding to each of the objects such that digitalcontent may be placed in an area in the FOV 3708 that aligns with thevirtual target line and falls at a focal plane of an intersectingobject. The user then may see the digital content when he focuses on theobject in the environment, which is at the same focal plane. Inembodiments, objects in line with the virtual target line may beestablished by comparison to mapped information of the surroundings.

In embodiments, the digital content that is in line with the virtualtarget line may not be displayed in the FOV until the eye position is inthe right position. This may be a predetermined process. For example,the system may be set up such that a particular piece of digital content(e.g. an advertisement, guidance information, object information, etc.)will appear in the event that the wearer looks at a certain object(s) inthe environment. A virtual target line(s) may be developed thatvirtually connects the wearer's eye with an object(s) in the environment(e.g. a building, portion of a building, mark on a building, gpslocation, etc.) and the virtual target line may be continually updateddepending on the position and viewing direction of the wearer (e.g. asdetermined through GPS, e-compass, IMU, etc.) and the position of theobject. When the virtual target line suggests that the wearer's pupil issubstantially aligned with the virtual target line or about to bealigned with the virtual target line, the digital content may bedisplayed in the FOV 3704.

In embodiments, the time spent looking along the virtual target lineand/or a particular portion of the FOV 3708 may indicate that the weareris interested in an object in the environment and/or digital contentbeing displayed. In the event there is no digital content beingdisplayed at the time a predetermined period of time is spent looking ata direction, digital content may be presented in the area of the FOV3708. The time spent looking at an object may be interpreted as acommand to display information about the object, for example. In otherembodiments, the content may not relate to the object and may bepresented because of the indication that the person is relativelyinactive. In embodiments, the digital content may be positioned inproximity to the virtual target line, but not in-line with it such thatthe wearer's view of the surroundings are not obstructed but informationcan augment the wearer's view of the surroundings. In embodiments, thetime spent looking along a target line in the direction of displayeddigital content may be an indication of interest in the digital content.This may be used as a conversion event in advertising. For example, anadvertiser may pay more for an add placement if the wearer of the HWC102 looks at a displayed advertisement for a certain period of time. Assuch, in embodiments, the time spent looking at the advertisement, asassessed by comparing eye position with the content placement, targetline or other appropriate position may be used to determine a rate ofconversion or other compensation amount due for the presentation.

An aspect of the invention relates to removing content from the FOV ofthe HWC 102 when the wearer of the HWC 102 apparently wants to view thesurrounding environments clearly. FIG. 38 illustrates a situation whereeye imagery suggests that the eye has or is moving quickly so thedigital content 3804 in the FOV 3808 is removed from the FOV 3808. Inthis example, the wearer may be looking quickly to the side indicatingthat there is something on the side in the environment that has grabbedthe wearer's attention. This eye movement 3802 may be captured througheye imaging techniques (e.g. as described herein) and if the movementmatches a predetermined movement (e.g. speed, rate, pattern, etc.) thecontent may be removed from view. In embodiments, the eye movement isused as one input and HWC movements indicated by other sensors (e.g. IMUin the HWC) may be used as another indication. These various sensormovements may be used together to project an event that should cause achange in the content being displayed in the FOV.

Another aspect of the present invention relates to determining a focalplane based on the wearer's eye convergence. Eyes are generallyconverged slightly and converge more when the person focuses onsomething very close. This is generally referred to as convergence. Inembodiments, convergence is calibrated for the wearer. That is, thewearer may be guided through certain focal plane exercises to determinehow much the wearer's eyes converge at various focal planes and atvarious viewing angles. The convergence information may then be storedin a database for later reference. In embodiments, a general table maybe used in the event there is no calibration step or the person skipsthe calibration step. The two eyes may then be imaged periodically todetermine the convergence in an attempt to understand what focal planethe wearer is focused on. In embodiments, the eyes may be imaged todetermine a virtual target line and then the eye's convergence may bedetermined to establish the wearer's focus, and the digital content maybe displayed or altered based thereon.

FIG. 39 illustrates a situation where digital content is moved 3902within one or both of the FOVs 3908 and 3910 to align with theconvergence of the eyes as determined by the pupil movement 3904. Bymoving the digital content to maintain alignment, in embodiments, theoverlapping nature of the content is maintained so the object appearsproperly to the wearer. This can be important in situations where 3Dcontent is displayed.

An aspect of the present invention relates to controlling the HWC 102based on events detected through eye imaging. A wearer winking,blinking, moving his eyes in a certain pattern, etc. may, for example,control an application of the HWC 102. Eye imaging (e.g. as describedherein) may be used to monitor the eye(s) of the wearer and once apre-determined pattern is detected an application control command may beinitiated.

An aspect of the invention relates to monitoring the health of a personwearing a HWC 102 by monitoring the wearer's eye(s). Calibrations may bemade such that the normal performance, under various conditions (e.g.lighting conditions, image light conditions, etc.) of a wearer's eyesmay be documented. The wearer's eyes may then be monitored through eyeimaging (e.g. as described herein) for changes in their performance.Changes in performance may be indicative of a health concern (e.g.concussion, brain injury, stroke, loss of blood, etc.). If detected thedata indicative of the change or event may be communicated from the HWC102.

Aspects of the present invention relate to security and access ofcomputer assets (e.g. the HWC itself and related computer systems) asdetermined through eye image verification. As discussed hereinelsewhere, eye imagery may be compared to known person eye imagery toconfirm a person's identity. Eye imagery may also be used to confirm theidentity of people wearing the HWCs 102 before allowing them to linktogether or share files, streams, information, etc.

A variety of use cases for eye imaging are possible based ontechnologies described herein. An aspect of the present inventionrelates to the timing of eye image capture. The timing of the capture ofthe eye image and the frequency of the capture of multiple images of theeye can vary dependent on the use case for the information gathered fromthe eye image. For example, capturing an eye image to identify the userof the HWC may be required only when the HWC has been turned ON or whenthe HWC determines that the HWC has been put onto a wearer's head tocontrol the security of the HWC and the associated information that isdisplayed to the user. Wherein, the orientation, movement pattern,stress or position of the earhorns (or other portions of the HWC) of theHWC can be used to determine that a person has put the HWC onto theirhead with the intention to use the HWC. Those same parameters may bemonitored in an effort to understand when the HWC is dismounted from theuser's head. This may enable a situation where the capture of an eyeimage for identifying the wearer may be completed only when a change inthe wearing status is identified. In a contrasting example, capturingeye images to monitor the health of the wearer may require images to becaptured periodically (e.g. every few seconds, minutes, hours, days,etc.). For example, the eye images may be taken in minute intervals whenthe images are being used to monitor the health of the wearer whendetected movements indicate that the wearer is exercising. In a furthercontrasting example, capturing eye images to monitor the health of thewearer for long-term effects may only require that eye images becaptured monthly. Embodiments of the invention relate to selection ofthe timing and rate of capture of eye images to be in correspondencewith the selected use scenario associated with the eye images. Theseselections may be done automatically, as with the exercise example abovewhere movements indicate exercise, or these selections may be setmanually. In a further embodiment, the selection of the timing and rateof eye image capture is adjusted automatically depending on the mode ofoperation of the HWC. The selection of the timing and rate of eye imagecapture can further be selected in correspondence with inputcharacteristics associated with the wearer including age and healthstatus, or sensed physical conditions of the wearer including heartrate, chemical makeup of the blood and eye blink rate.

FIG. 40 illustrates an embodiment in which digital content presented ina see-through FOV is positioned based on the speed in which the weareris moving. When the person is not moving, as measured by sensor(s) inthe HWC 102 (e.g. IMU, GPS based tracking, etc.), digital content may bepresented at the stationary person content position 4004. The contentposition 4004 is indicated as being in the middle of the see-through FOV4002; however, this is meant to illustrate that the digital content ispositioned within the see-through FOV at a place that is generallydesirable knowing that the wearer is not moving and as such the wearer'ssurrounding see through view can be somewhat obstructed. So, thestationary person content position, or neutral position, may not becentered in the see-through FOV; it may be positioned somewhere in thesee-through FOV deemed desirable and the sensor feedback may shift thedigital content from the neutral position. The movement of the digitalcontent for a quickly moving person is also shown in FIG. 40 wherein asthe person turns their head to the side, the digital content moves outof the see-through FOV to content position 4008 and then moves back asthe person turns their head back. For a slowly moving person, the headmovement can be more complex and as such the movement of the digitalcontent in an out of the see-through FOV can follow a path such as thatshown by content position 4010.

In embodiments, the sensor that assesses the wearer's movements may be aGPS sensor, IMU, accelerometer, etc. The content position may be shiftedfrom a neutral position to a position towards a side edge of the fieldof view as the forward motion increases. The content position may beshifted from a neutral position to a position towards a top or bottomedge of the field of view as the forward motion increases. The contentposition may shift based on a threshold speed of the assessed motion.The content position may shift linearly based on the speed of theforward motion. The content position may shift non-linearly based on thespeed of the forward motion. The content position may shift outside ofthe field of view. In embodiments, the content is no longer displayed ifthe speed of movement exceeds a predetermined threshold and will bedisplayed again once the forward motion slows.

In embodiments, the content position may generally be referred to asshifting; it should be understood that the term shifting encompasses aprocess where the movement from one position to another within thesee-through FOV or out of the FOV is visible to the wearer (e.g. thecontent appears to slowly or quickly move and the user perceives themovement itself) or the movement from one position to another may not bevisible to the wearer (e.g. the content appears to jump in adiscontinuous fashion or the content disappears and then reappears inthe new position).

Another aspect of the present invention relates to removing the contentfrom the field of view or shifting it to a position within the field ofview that increases the wearer's view of the surrounding environmentwhen a sensor causes an alert command to be issued. In embodiments, thealert may be due to a sensor or combination of sensors that sense acondition above a threshold value. For example, if an audio sensordetects a loud sound of a certain pitch, content in the field of viewmay be removed or shifted to provide a clear view of the surroundingenvironment for the wearer. In addition to the shifting of the content,in embodiments, an indication of why the content was shifted may bepresented in the field of view or provided through audio feedback to thewearer. For instance, if a carbon monoxide sensor detects a highconcentration in the area, content in the field of view may be shiftedto the side of the field of view or removed from the field of view andan indication may be provided to the wearer that there is a highconcentration of carbon monoxide in the area. This new information, whenpresented in the field of view, may similarly be shifted within oroutside of the field of view depending on the movement speed of thewearer.

FIG. 41 illustrates how content may be shifted from a neutral position4104 to an alert position 4108. In this embodiment, the content isshifted outside of the see-through FOV 4102. In other embodiments, thecontent may be shifted as described herein.

Another aspect of the present invention relates to identification ofvarious vectors or headings related to the HWC 102, along with sensorinputs, to determine how to position content in the field of view. Inembodiments, the speed of movement of the wearer is detected and used asan input for position of the content and, depending on the speed, thecontent may be positioned with respect to a movement vector or heading(i.e. the direction of the movement), or a sight vector or heading (i.e.the direction of the wearer's sight direction). For example, if thewearer is moving very fast the content may be positioned within thefield of view with respect to the movement vector because the wearer isonly going to be looking towards the sides of himself periodically andfor short periods of time. As another example, if the wearer is movingslowly, the content may be positioned with respect to the sight headingbecause the user may more freely be shifting his view from side to side.

FIG. 42 illustrates two examples where the movement vector may effectcontent positioning. Movement vector A 4202 is shorter than movementvector B 4210 indicating that the forward speed and/or acceleration ofmovement of the person associated with movement vector A 4202 is lowerthan the person associated with movement vector B 4210. Each person isalso indicated as having a sight vector or heading 4208 and 4212. Thesight vectors A 4208 and B 4210 are the same from a relativeperspective. The white area inside of the black triangle in front ofeach person is indicative of how much time each person likely spendslooking at a direction that is not in line with the movement vector. Thetime spent looking off angle A 4204 is indicated as being more than thatof the time spent looking off angle B 4214. This may be because themovement vector speed A is lower than movement vector speed B. Thefaster the person moves forward the more the person tends to look in theforward direction, typically. The FOVs A 4218 and B 4222 illustrate howcontent may be aligned depending on the movement vectors 4202 and 4210and sight vectors 4208 and 4212. FOV A 4218 is illustrated as presentingcontent in-line with the sight vector 4220. This may be due to the lowerspeed of the movement vector A 4202. This may also be due to theprediction of a larger amount of time spent looking off angle A 4204.FOV B 4222 is illustrated as presenting content in line with themovement vector 4224. This may be due to the higher speed of movementvector B 4210. This may also be due to the prediction of a shorteramount of time spent looking off angle B 4214.

Another aspect of the present invention relates to damping a rate ofcontent position change within the field of view. As illustrated in FIG.43, the sight vector may undergo a rapid change 4304. This rapid changemay be an isolated event or it may be made at or near a time when othersight vector changes are occurring. The wearer's head may be turningback and forth for some reason. In embodiments, the rapid successivechanges in sight vector may cause a damped rate of content positionchange 4308 within the FOV 4302. For example, the content may bepositioned with respect to the sight vector, as described herein, andthe rapid change in sight vector may normally cause a rapid contentposition change; however, since the sight vector is successivelychanging, the rate of position change with respect to the sight vectormay be damped, slowed, or stopped. The position rate change may bealtered based on the rate of change of the sight vector, average of thesight vector changes, or otherwise altered.

Another aspect of the present invention relates to simultaneouslypresenting more than one content in the field of view of a see-throughoptical system of a HWC 102 and positioning one content with the sightheading and one content with the movement heading. FIG. 44 illustratestwo FOV's A 4414 and B 4420, which correspond respectively to the twoidentified sight vectors A 4402 and B 4404. FIG. 44 also illustrates anobject in the environment 4408 at a position relative to the sightvectors A 4402 and B 4404. When the person is looking along sight vectorA 4402, the environment object 4408 can be seen through the field ofview A 4414 at position 4412. As illustrated, sight heading alignedcontent is presented as TEXT in proximity with the environment object4412. At the same time, other content 4418 is presented in the field ofview A 4414 at a position aligned in correspondence with the movementvector. As the movement speed increases, the content 4418 may shift asdescribed herein. When the sight vector of the person is sight vector B4404 the environmental object 4408 is not seen in the field of view B4420. As a result, the sight aligned content 4410 is not presented infield of view B 4420; however, the movement aligned content 4419 ispresented and is still dependent on the speed of the motion.

FIG. 45 shows an example set of data for a person moving through anenvironment over a path that starts with a movement heading of 0 degreesand ends with a movement heading of 114 degrees during which time thespeed of movement varies from 0 m/sec to 20 m/sec. The sight heading canbe seen to vary on either side of the movement heading while moving asthe person looks from side to side. Large changes in sight heading occurwhen the movement speed is 0 m/sec when the person is standing still,followed by step changes in movement heading.

Embodiments provide a process for determining the display heading thattakes into account the way a user moves through an environment andprovides a display heading that makes it easy for the user to find thedisplayed information while also providing unencumbered see-throughviews of the environment in response to different movements, speed ofmovement or different types of information being displayed.

FIG. 46 illustrates a see-through view as may be seen when using a HWCwherein information is overlaid onto a see-through view of theenvironment. The tree and the building are actually in the environmentand the text is displayed in the see-through display such that itappears overlaid on the environment. In addition to text informationsuch as, for example, instructions and weather information, someaugmented reality information is shown that relates to nearby objects inthe environment.

In an embodiment, the display heading is determined based on speed ofmovement. At low speeds, the display heading may be substantially thesame as the sight heading while at high speed the display heading may besubstantially the same as the movement heading. In embodiments, as longas the user remains stationary, the displayed information is presenteddirectly in front of the user and HWC. However, as the movement speedincreases (e.g. above a threshold or continually, etc.) the displayheading becomes substantially the same as the movement headingregardless of the direction the user is looking, so that when the userlooks in the direction of movement, the displayed information isdirectly in front of the user and HMD and when the user looks to theside the displayed information is not visible.

Rapid changes in sight heading can be followed by a slower change in thedisplay heading to provide a damped response to head rotation.Alternatively, the display heading can be substantially the timeaveraged sight heading so that the displayed information is presented ata heading that is in the middle of a series of sight headings over aperiod of time. In this embodiment, if the user stops moving their head,the display heading gradually becomes the same as the sight heading andthe displayed information moves into the display field of view in frontof the user and HMD. In embodiments, when there is a high rate of sightheading change, the process delays the effect of the time averaged sightheading on the display heading. In this way, the effect of rapid headmovements on display heading is reduced and the positioning of thedisplayed information within the display field of view is stabilizedlaterally.

In another embodiment, display heading is determined based on speed ofmovement where at high-speed, the display heading is substantially thesame as the movement heading. At mid-speed the display heading issubstantially the same as a time averaged sight heading so that rapidhead rotations are damped out and the display heading is in the middleof back and forth head movements.

In yet another embodiment, the type of information being displayed isincluded in determining how the information should be displayed.Augmented reality information that is connected to objects in theenvironment is given a display heading that substantially matches thesight heading. In this way, as the user rotates their head, augmentedreality information comes into view that is related to objects that arein the see-through view of the environment. At the same time,information that is not connected to objects in the environment is givena display heading that is determined based on the type of movements andspeed of movements as previously described in this specification.

In yet a further embodiment, when the speed of movement is determined tobe above a threshold, the information displayed is moved downward in thedisplay field of view so that the upper portion of the display field ofview has less information or no information displayed to provide theuser with an unencumbered see-through view of the environment.

FIGS. 47 and 48 show illustrations of a see-through view includingoverlaid displayed information. FIG. 47 shows the see-through viewimmediately after a rapid change in sight heading from the sight headingassociated with the see-through view shown in FIG. 46 wherein the changein sight heading comes from a head rotation. In this case, the displayheading is delayed. FIG. 48 shows how at a later time, the displayheading catches up to the sight heading. The augmented realityinformation remains in positions within the display field of view wherethe association with objects in the environment can be readily made bythe user.

FIG. 49 shows an illustration of a see-through view example includingoverlaid displayed information that has been shifted downward in thedisplay field of view to provide an unencumbered see-through view in theupper portion of the see-through view. At the same time, augmentedreality labels have been maintained in locations within the displayfield of view so they can be readily associated with objects in theenvironment.

In a further embodiment, in an operating mode such as when the user ismoving in an environment, digital content is presented at the side ofthe user's see-through FOV so that the user can only view the digitalcontent by turning their head. In this case, when the user is lookingstraight ahead, such as when the movement heading matches the sightheading, the see-through view FOV does not include digital content. Theuser then accesses the digital content by turning their head to the sidewhereupon the digital content moves laterally into the user'ssee-through FOV. In another embodiment, the digital content is ready forpresentation and will be presented if an indication for its presentationis received. For example, the information may be ready for presentationand if the sight heading or predetermined position of the HWC 102 isachieved the content may then be presented. The wearer may look to theside and the content may be presented. In another embodiment, the usermay cause the content to move into an area in the field of view bylooking in a direction for a predetermined period of time, blinking,winking, or displaying some other pattern that can be captured througheye imaging technologies (e.g. as described herein elsewhere).

In yet another embodiment, an operating mode is provided wherein theuser can define sight headings wherein the associated see-through FOVincludes digital content or does not include digital content. In anexample, this operating mode can be used in an office environment wherewhen the user is looking at a wall digital content is provided withinthe FOV, whereas when the user is looking toward a hallway, the FOV isunencumbered by digital content. In another example, when the user islooking horizontally digital content is provided within the FOV, butwhen the user looks down (e.g. to look at a desktop or a cellphone) thedigital content is removed from the FOV.

Another aspect of the present invention relates to collecting and usingeye position and sight heading information. Head worn computing withmotion heading, sight heading, and/or eye position prediction (sometimesreferred to as “eye heading” herein) may be used to identify what awearer of the HWC 102 is apparently interested in and the informationmay be captured and used. In embodiments, the information may becharacterized as viewing information because the information apparentlyrelates to what the wearer is looking at. The viewing information may beused to develop a personal profile for the wearer, which may indicatewhat the wearer tends to look at. The viewing information from severalor many HWC's 102 may be captured such that group or crowd viewingtrends may be established. For example, if the movement heading andsight heading are known, a prediction of what the wearer is looking atmay be made and used to generate a personal profile or portion of acrowd profile. In another embodiment, if the eye heading and location,sight heading and/or movement heading are known, a prediction of what isbeing looked at may be predicted. The prediction may involveunderstanding what is in proximity of the wearer and this may beunderstood by establishing the position of the wearer (e.g. through GPSor other location technology) and establishing what mapped objects areknown in the area. The prediction may involve interpreting imagescaptured by the camera or other sensors associated with the HWC 102. Forexample, if the camera captures an image of a sign and the camera isin-line with the sight heading, the prediction may involve assessing thelikelihood that the wearer is viewing the sign. The prediction mayinvolve capturing an image or other sensory information and thenperforming object recognition analysis to determine what is beingviewed. For example, the wearer may be walking down a street and thecamera that is in the HWC 102 may capture an image and a processor,either on-board or remote from the HWC 102, may recognize a face,object, marker, image, etc. and it may be determined that the wearer mayhave been looking at it or towards it.

FIG. 50 illustrates a cross section of an eyeball of a wearer of an HWCwith focus points that can be associated with the eye imaging system ofthe invention. The eyeball 5010 includes an iris 5012 and a retina 5014.Because the eye imaging system of the invention provides coaxial eyeimaging with a display system, images of the eye can be captured from aperspective directly in front of the eye and inline with where thewearer is looking. In embodiments of the invention, the eye imagingsystem can be focused at the iris 5012 and/or the retina 5014 of thewearer, to capture images of the external surface of the iris 5012 orthe internal portions of the eye, which includes the retina 5014. FIG.50 shows light rays 5020 and 5025 that are respectively associated withcapturing images of the iris 5012 or the retina 5014 wherein the opticsassociated with the eye imaging system are respectively focused at theiris 5012 or the retina 5014. Illuminating light can also be provided inthe eye imaging system to illuminate the iris 5012 or the retina 5014.FIG. 51 shows an illustration of an eye including an iris 5130 and asclera 5125. In embodiments, the eye imaging system can be used tocapture images that include the iris 5130 and portions the sclera 5125.The images can then be analyzed to determine color, shapes and patternsthat are associated with the user. In further embodiments, the focus ofthe eye imaging system is adjusted to enable images to be captured ofthe iris 5012 or the retina 5014. Illuminating light can also beadjusted to illuminate the iris 5012 or to pass through the pupil of theeye to illuminate the retina 5014. The illuminating light can be visiblelight to enable capture of colors of the iris 5012 or the retina 5014,or the illuminating light can be ultraviolet (e.g. 340 nm), nearinfrared (e.g. 850 nm) or mid-wave infrared (e.g. 5000 nm) light toenable capture of hyperspectral characteristics of the eye.

FIG. 53 illustrates a display system that includes an eye imagingsystem. The display system includes a polarized light source 2958, a DLP2955, a quarter wave film 2957 and a beam splitter plate 5345. The eyeimaging system includes a camera 3280, illuminating lights 5355 and beamsplitter plate 5345. Where the beam splitter plate 5345 can be areflective polarizer on the side facing the polarized light source 2958and a hot mirror on the side facing the camera 3280. Wherein the hotmirror reflects infrared light (e.g. wavelengths 700 to 2000 nm) andtransmits visible light (e.g. wavelengths 400 to 670 nm). The beamsplitter plate 5345 can be comprised of multiple laminated films, asubstrate film with coatings or a rigid transparent substrate with filmson either side. By providing a reflective polarizer on the one side, thelight from the polarized light source 2958 is reflected toward the DLP2955 where it passes through the quarter wave film 2957 once, isreflected by the DLP mirrors in correspondence with the image contentbeing displayed by the DLP 2955 and then passes back through the quarterwave film 2957. In so doing, the polarization state of the light fromthe polarized light source is changed, so that it is transmitted by thereflective polarizer on the beam splitter plate 5345 and the image light2971 passes into the lower optics module 204 where the image isdisplayed to the user. At the same time, infrared light 5357 from theilluminating lights 5355 is reflected by the hot mirror so that itpasses into the lower optics module 204 where it illuminates the user'seye. Portions of the infrared light 2969 are reflected by the user's eyeand this light passes back through the lower optics module 204, isreflected by the hot mirror on the beam splitter plate 5345 and iscaptured by the camera 3280. In this embodiment, the image light 2971 ispolarized while the infrared light 5357 and 2969 can be unpolarized. Inan embodiment, the illuminating lights 5355 provide two differentinfrared wavelengths and eye images are captured in pairs, wherein thepairs of eye images are analyzed together to improve the accuracy ofidentification of the user based on iris analysis.

FIG. 54 shows an illustration of a further embodiment of a displaysystem with an eye imaging system. In addition to the features of FIG.53, this system includes a second camera 5460. Wherein the second camera5460 is provided to capture eye images in the visible wavelengths.Illumination of the eye can be provided by the displayed image or bysee-through light from the environment. Portions of the displayed imagecan be modified to provide improved illumination of the user's eye whenimages of the eye are to be captured such as by increasing thebrightness of the displayed image or increasing the white areas withinthe displayed image. Further, modified displayed images can be presentedbriefly for the purpose of capturing eye images and the display of themodified images can be synchronized with the capture of the eye images.As shown in FIG. 54, visible light 5467 is polarized when it is capturedby the second camera 5460 since it passes through the beam splitter 5445and the beam splitter 5445 is a reflective polarizer on the side facingthe second camera 5460. In this eye imaging system, visible eye imagescan be captured by the second camera 5460 at the same time that infraredeye images are captured by the camera 3280. Wherein, the characteristicsof the camera 3280 and the second camera 5460 and the associatedrespective images captured can be different in terms of resolution andcapture rate.

FIGS. 52a and 52b illustrate captured images of eyes where the eyes areilluminated with structured light patterns. In FIG. 52a , an eye 5220 isshown with a projected structured light pattern 5230, where the lightpattern is a grid of lines. A light pattern of such as 5230 can beprovided by the light source 5355 show in FIG. 53 by including adiffractive or a refractive device to modify the light 5357 as are knownby those skilled in the art. A visible light source can also be includedfor the second camera 5460 shown in FIG. 54 which can include adiffractive or refractive to modify the light 5467 to provide a lightpattern. FIG. 52b illustrates how the structured light pattern of 5230becomes distorted to 5235 when the user's eye 5225 looks to the side.This distortion comes from the fact that the human eye is not sphericalin shape, instead the iris sticks out slightly from the eyeball to forma bump in the area of the iris. As a result, the shape of the eye andthe associated shape of the reflected structured light pattern isdifferent depending on which direction the eye is pointed, when imagesof the eye are captured from a fixed position. Changes in the structuredlight pattern can subsequently be analyzed in captured eye images todetermine the direction that the eye is looking.

The eye imaging system can also be used for the assessment of aspects ofhealth of the user. In this case, information gained from analyzingcaptured images of the iris 5012 is different from information gainedfrom analyzing captured images of the retina 5014. Where images of theretina 5014 are captured using light 5357 that illuminates the innerportions of the eye including the retina 5014. The light 5357 can bevisible light, but in an embodiment, the light 5357 is infrared light(e.g. wavelength 1 to 5 microns) and the camera 3280 is an infraredlight sensor (e.g. an InGaAs sensor) or a low resolution infrared imagesensor that is used to determine the relative amount of light 5357 thatis absorbed, reflected or scattered by the inner portions of the eye.Wherein the majority of the light that is absorbed, reflected orscattered can be attributed to materials in the inner portion of the eyeincluding the retina where there are densely packed blood vessels withthin walls so that the absorption, reflection and scattering are causedby the material makeup of the blood. These measurements can be conductedautomatically when the user is wearing the HWC, either at regularintervals, after identified events or when prompted by an externalcommunication. In a preferred embodiment, the illuminating light is nearinfrared or mid infrared (e.g. 0.7 to 5 microns wavelength) to reducethe chance for thermal damage to the wearer's eye. In anotherembodiment, the polarizer 3285 is antireflection coated to reduce anyreflections from this surface from the light 5357, the light 2969 or thelight 3275 and thereby increase the sensitivity of the camera 3280. In afurther embodiment, the light source 5355 and the camera 3280 togethercomprise a spectrometer wherein the relative intensity of the lightreflected by the eye is analyzed over a series of narrow wavelengthswithin the range of wavelengths provided by the light source 5355 todetermine a characteristic spectrum of the light that is absorbed,reflected or scattered by the eye. For example, the light source 5355can provide a broad range of infrared light to illuminate the eye andthe camera 3280 can include: a grating to laterally disperse thereflected light from the eye into a series of narrow wavelength bandsthat are captured by a linear photodetector so that the relativeintensity by wavelength can be measured and a characteristic absorbancespectrum for the eye can be determined over the broad range of infrared.In a further example, the light source 5355 can provide a series ofnarrow wavelengths of light (ultraviolet, visible or infrared) tosequentially illuminate the eye and camera 3280 includes a photodetectorthat is selected to measure the relative intensity of the series ofnarrow wavelengths in a series of sequential measurements that togethercan be used to determine a characteristic spectrum of the eye. Thedetermined characteristic spectrum is then compared to knowncharacteristic spectra for different materials to determine the materialmakeup of the eye. In yet another embodiment, the illuminating light5357 is focused on the retina 5014 and a characteristic spectrum of theretina 5014 is determined and the spectrum is compared to known spectrafor materials that may be present in the user's blood. For example, inthe visible wavelengths 540 nm is useful for detecting hemoglobin and660 nm is useful for differentiating oxygenated hemoglobin. In a furtherexample, in the infrared, a wide variety of materials can be identifiedas is known by those skilled in the art, including: glucose, urea,alcohol and controlled substances. FIG. 55 shows a series of examplespectrum for a variety of controlled substances as measured using a formof infrared spectroscopy (ThermoScientific Application Note 51242, by C.Petty, B. Garland and the Mesa Police Department Forensic Laboratory,which is hereby incorporated by reference herein). FIG. 56 shows aninfrared absorbance spectrum for glucose (Hewlett Packard Company 1999,G. Hopkins, G. Mauze; “In-vivo NIR Diffuse-reflectance TissueSpectroscopy of Human Subjects,” which is hereby incorporated byreference herein). U.S. Pat. No. 6,675,030, which is hereby incorporatedby reference herein, provides a near infrared blood glucose monitoringsystem that includes infrared scans of a body part such as a foot.United States Patent publication 2006/0183986, which is herebyincorporated by reference herein, provides a blood glucose monitoringsystem including a light measurement of the retina. Embodiments of thepresent invention provide methods for automatic measurements of specificmaterials in the user's blood by illuminating at one or more narrowwavelengths into the iris of the wearer's eye and measuring the relativeintensity of the light reflected by the eye to identify the relativeabsorbance spectrum and comparing the measured absorbance spectrum withknown absorbance spectra for the specific material, such as illuminatingat 540 and 660 nm to determine the level of hemoglobin present in theuser's blood.

Another aspect of the present invention relates to collecting and usingeye position and sight heading information. Head worn computing withmotion heading, sight heading, and/or eye position prediction (sometimesreferred to as “eye heading” herein) may be used to identify what awearer of the HWC 102 is apparently interested in and the informationmay be captured and used. In embodiments, the information may becharacterized as viewing information because the information apparentlyrelates to what the wearer is looking at. The viewing information may beused to develop a personal profile for the wearer, which may indicatewhat the wearer tends to look at. The viewing information from severalor many HWC's 102 may be captured such that group or crowd viewingtrends may be established. For example, if the movement heading andsight heading are known, a prediction of what the wearer is looking atmay be made and used to generate a personal profile or portion of acrowd profile. In another embodiment, if the eye heading and location,sight heading and/or movement heading are known, a prediction of what isbeing looked at may be predicted. The prediction may involveunderstanding what is in proximity of the wearer and this may beunderstood by establishing the position of the wearer (e.g. through GPSor other location technology) and establishing what mapped objects areknown in the area. The prediction may involve interpreting imagescaptured by the camera or other sensors associated with the HWC 102. Forexample, if the camera captures an image of a sign and the camera isin-line with the sight heading, the prediction may involve assessing thelikelihood that the wearer is viewing the sign. The prediction mayinvolve capturing an image or other sensory information and thenperforming object recognition analysis to determine what is beingviewed. For example, the wearer may be walking down a street and thecamera that is in the HWC 102 may capture an image and a processor,either on-board or remote from the HWC 102, may recognize a face,object, marker, image, etc. and it may be determined that the wearer mayhave been looking at it or towards it.

In a further embodiment, a method is provided for identifying changes inthe focus distance associated with the user's eye by measuring changesin the size of the eye glint. Where an ability to identify changes inthe focus distance for the user's eye can be helpful for determiningwhat the user is looking at in the surrounding environment when using anHMD that provides a see-through view of the surrounding environment isbeing used. Identifying changes in the focus distance for the user's eyecan also be useful for automatic display mode selection (e.g. selectingwhether the displayed image should be bright or dim) by determiningwhether the user is looking at the displayed image content, where thefocus distance of the user's eye matches the focus distance of thedisplayed image, or the user is looking at the surrounding environment,where the focus distance of the user's eye is different from the focusdistance of the displayed image.

The eye lens in a human eye changes spherical radius to provide changesin the focus distance or accommodation (see S. Plainis, W. Charman, I.Pallikaris, “The Physiologic Mechanism of Accommodation”, Cataract &Refractive Surgery Today Europe, April 2014, pp 23-29). FIG. 56e shows achart of the measured anterior and posterior spherical radii of the eyeof a 29 year old person over a 0 to 6 diopter range of accommodation aspresented in the paper by Plainis. This change in accommodationcorresponds to a focus distance change from infinity to approximately0.16 meter based on the diopter change in focal length of the eye lens,where the relationship between focal length of a lens and diopter isgiven in Equation 1 below.

FL=1/δ  Equation 1

Where FL is the focal length of the lens in meters and d is the diopterrating of the lens. The anterior surface of the eye lens is covered bythe cornea and the iris so that the surface of the eye lens is notexposed to the environment, however changes in spherical radius of theeye lens are accompanied by changes in spherical radius of the externalsurface of the cornea. These changes in spherical radius of the corneaaffect the size of the reflected eye glint that can be seen on thesurface of the eye. As the spherical radius of the eye lens decreases toprovide a higher level of accommodation, the external spherical radiusof the cornea decreases as well which causes the size of the reflectedeye glint to decrease. Similarly, as the spherical radius of the eyelens increases to provide a lower level of accommodation, the externalspherical radius of the cornea increases which causes the size of thereflected eye glint to increase. As such, measurements of the size ofthe eye glint can be used to identify changes in the focus distance of auser's eye. Where measurements of the size of the eye glint can beprovided from images of the user's eye captured by an eye camera.

To provide for a reliable detection of eye glint size, a light source ofconstant size should be provided that is subsequently reflected by theexternal surface of the cornea in the form of an eye glint. FIGS. 56aand 56b show example eye glints 5612 and 5614 produced from a reflectedillumination source such as an LED that is used to illuminate the user'seye for eye imaging for purposes such as eye tracking or irisidentification. In this case, the LED is a round illumination source, sothe eye glint is also round. FIG. 56a shows a larger diameter eye glint5612 within the image of the eye 5610 that corresponds to a larger focusdistance than indicated by the smaller diameter eye glint 5614 shown inFIG. 56b . The LED illumination source can provide visible wavelengthlight or infrared wavelength light to provide an eye glint and toprovide illumination for eye imaging as long as the eye camera in theHMD is capable of capturing images of the eye that include thewavelengths provided by the illumination source (e.g. as described inthe eye imaging and eye illumination systems disclosed herein). FIGS.56c and 56d show another example of eye glints 5616 and 5618 where theillumination source is the displayed image so that the eye glints 5616and 5618 are rectangular in shape. FIG. 56c shows a larger eye glint5616 than the eye glint 5618 shown in FIG. 56d , which indicates thatthe focus distance of the eye 5610 in FIG. 56c is larger than the focusdistance of the eye 5610 shown in FIG. 56c . In embodiments, the lightemitted to be reflected from the eye may be in a known pattern sochanges in the pattern can be assessed for focus changes.

Measurements of the size of an eye glint from a known illuminationsource are readily accomplished with an eye camera in the HMD (e.g. asdisclosed herein). The resolution of the size of the eye glint isdetermined by the angular size of a pixel (e.g. eye camera field ofview/horizontal number of pixels in an eye image) in an eye image fromthe eye camera. As such it is advantageous to have more pixels in asmaller field of view in the eye camera. This method of identifyingchanges in focus distance associated with the user's eye can be usedwith any type of optics for a HMD for example: including refractiveoptics, reflective optics, holographic optics, beam splitter optics,waveguide optics, grating optics or multiple reflector optics, providedthe optics include an eye camera for imaging the user's eye.

In a further embodiment, the illumination source that provides thereflected eye glint can provide structured light with a pattern. Thesize or spacing of the pattern can then be used to identify changes infocus distance.

In another embodiment, identified changes in the focus distance of theuser's eye are used to identify a convergence distance for the displayedimage. Providing a convergence distance and focus distance for thedisplayed image that matches the focus distance of the user's eye can beused for displaying images that are watched intensely such as a movie.Conversely, a convergence distance and focus distance for the displayedimage that is different from the focus distance of the user's eye can beused to provide displayed image that is not watched intensely such as abattery indicator, directional information, assembly instructions oraugmented reality objects.

In embodiments, glint size and placement measurements may be used inconjunction with other techniques such as convergence measurements todetermine the user's focus distance.

FIG. 57 illustrates a scene where a person is walking with a HWC 102mounted on his head. In this scene, the person's geo-spatial location5704 is known through a GPS sensor, which could be another locationsystem, and his movement heading, sight heading 5714 and eye heading5702 are known and can be recorded (e.g. through systems describedherein). There are objects and a person in the scene. Person 5712 may berecognized by the wearer's HWC 102 system, the person may be mapped(e.g. the person's GPS location may be known or recognized), orotherwise known. The person may be wearing a garment or device that isrecognizable. For example, the garment may be of a certain style and theHWC may recognize the style and record it's viewing. The scene alsoincludes a mapped object 5718 and a recognized object 5720. As thewearer moves through the scene, the sight and/or eye headings may berecorded and communicated from the HWC 102. In embodiments, the timethat the sight and/or eye heading maintains a particular position may berecorded. For example, if a person appears to look at an object orperson for a predetermined period of time (e.g. 2 seconds or longer),the information may be communicated as gaze persistence information asan indication that the person may have been interested in the object.

In embodiments, sight headings may be used in conjunction with eyeheadings or eye and/or sight headings may be used alone. Sight headingscan do a good job of predicting what direction a wearer is lookingbecause many times the eyes are looking forward, in the same generaldirection as the sight heading. In other situations, eye headings may bea more desirable metric because the eye and sight headings are notalways aligned. In embodiments herein examples may be provided with theterm “eye/sight” heading, which indicates that either or both eyeheading and sight heading may be used in the example.

FIG. 58 illustrates a system for receiving, developing and usingmovement heading, sight heading, eye heading and/or persistenceinformation from HWC(s) 102. The server 5804 may receive heading or gazepersistence information, which is noted as persistence information 5802,for processing and/or use. The heading and/or gaze persistenceinformation may be used to generate a personal profile 5808 and/or agroup profile 5810. The personal profile 5718 may reflect the wearer'sgeneral viewing tendencies and interests. The group profile 5810 may bean assemblage of different wearer's heading and persistence informationto create impressions of general group viewing tendencies and interests.The group profile 5810 may be broken into different groups based onother information such as gender, likes, dislikes, biographicalinformation, etc. such that certain groups can be distinguished fromother groups. This may be useful in advertising because an advertisermay be interested in what a male adult sports go'er is generally lookingat as oppose to a younger female. The profiles 5808 and 5810 and rawheading and persistence information may be used by retailers 5814,advertisers 5818, trainers, etc. For example, an advertiser may have anadvertisement posted in an environment and may be interested in knowinghow many people look at the advertisement, how long they look at it andwhere they go after looking at it. This information may be used asconversion information to assess the value of the advertisement and thusthe payment to be received for the advertisement.

In embodiments, the process involves collecting eye and/or sight headinginformation from a plurality of head-worn computers that come intoproximity with an object in an environment. For example, a number ofpeople may be walking through an area and each of the people may bewearing a head worn computer with the ability to track the position ofthe wearer's eye(s) as well as possibly the wearer's sight and movementheadings. The various HWC wearing individuals may then walk, ride, orotherwise come into proximity with some object in the environment (e.g.a store, sign, person, vehicle, box, bag, etc.). When each person passesby or otherwise comes near the object, the eye imaging system maydetermine if the person is looking towards the object. All of theeye/sight heading information may be collected and used to formimpressions of how the crowd reacted to the object. A store may berunning a sale and so the store may put out a sign indicating such. Thestoreowners and managers may be very interested to know if anyone islooking at their sign. The sign may be set as the object of interest inthe area and as people navigate near the sign, possibly determined bytheir GPS locations, the eye/sight heading determination system mayrecord information relative to the environment and the sign. Once, oras, the eye/sight heading information is collected and associationsbetween the eye headings and the sign are determined, feedback may besent back to the storeowner, managers, advertiser, etc. as an indicationof how well their sign is attracting people. In embodiments, the sign'seffectiveness at attracting people's attention, as indicated through theeye/sight headings, may be considered a conversion metric and impact theeconomic value of the sign and/or the signs placement.

In embodiments, a map of the environment with the object may begenerated by mapping the locations and movement paths of the people inthe crowd as they navigate by the object (e.g. the sign). Layered onthis map may be an indication of the various eye/sight headings. Thismay be useful in indicating wear people were in relation to the objectwhen then viewed they object. The map may also have an indication of howlong people looked at the object from the various positions in theenvironment and where they went after seeing the object.

In embodiments, the process involves collecting a plurality of eye/sightheadings from a head-worn computer, wherein each of the plurality ofeye/sight headings is associated with a different pre-determined objectin an environment. This technology may be used to determine which of thedifferent objects attracts more of the person's attention. For example,if there are three objects placed in an environment and a person entersthe environment navigating his way through it, he may look at one ormore of the objects and his eye/sight heading may persist on one or moreobjects longer than others. This may be used in making or refining theperson's personal attention profile and/or it may be used in connectionwith other such people's data on the same or similar objects todetermine an impression of how the population or crowd reacts to theobjects. Testing advertisements in this way may provide good feedback ofits effectiveness.

In embodiments, the process may involve capturing eye/sight headingsonce there is substantial alignment between the eye/sight heading and anobject of interest. For example, the person with the HWC may benavigating through an environment and once the HWC detects substantialalignment or the projected occurrence of an upcoming substantialalignment between the eye/sight heading and the object of interest, theoccurrence and/or persistence may be recorded for use.

In embodiments, the process may involve collecting eye/sight headinginformation from a head-worn computer and collecting a captured imagefrom the head-worn computer that was taken at substantially the sametime as the eye/sight heading information was captured. These two piecesof information may be used in conjunction to gain an understanding ofwhat the wearer was looking at and possibly interested in. The processmay further involve associating the eye/sight heading information withan object, person, or other thing found in the captured image. This mayinvolve processing the captured image looking for objects or patterns.In embodiments, gaze time or persistence may be measured and used inconjunction with the image processing. The process may still involveobject and/or pattern recognition, but it may also involve attempting toidentify what the person gazed at for the period of time by moreparticularly identifying a portion of the image in conjunction withimage processing.

In embodiments, the process may involve setting a pre-determinedeye/sight heading from a pre-determined geospatial location and usingthem as triggers. In the event that a head worn computer enters thegeospatial location and an eye/sight heading associated with the headworn computer aligns with the pre-determined eye/sight heading, thesystem may collect the fact that there was an apparent alignment and/orthe system may record information identifying how long the eye/sightheading remains substantially aligned with the pre-determined eye/sightheading to form a persistence statistic. This may eliminate or reducethe need for image processing as the triggers can be used without havingto image the area. In other embodiments, image capture and processing isperformed in conjunction with the triggers. In embodiments, the triggersmay be a series a geospatial locations with corresponding eye/sightheadings such that many spots can be used as triggers that indicate whena person entered an area in proximity to an object of interest and/orwhen that person actually appeared to look at the object.

In embodiments, eye imaging may be used to capture images of both eyesof the wearer in order to determine the amount of convergence of theeyes (e.g. through technologies described herein elsewhere) to get anunderstanding of what focal plane is being concentrated on by thewearer. For example, if the convergence measurement suggests that thefocal plane is within 15 feet of the wearer, than, even though theeye/sight headings may align with an object that is more than 15 feetaway it may be determined that the wearer was not looking at the object.If the object were within the 15 foot suggested focal plane, thedetermination may be that the wearer was looking at the object. FIG. 59illustrates an environmentally position locked digital content 5912 thatis indicative of a person's location 5902. In this disclosure the term“BlueForce” is generally used to indicate team members or members forwhich geo-spatial locations are known and can be used. In embodiments,“BlueForce” is a term to indicate members of a tactical arms team (e.g.a police force, secret service force, security force, military force,national security force, intelligence force, etc.). In many embodimentsherein one member may be referred to as the primary or first BlueForcemember and it is this member, in many described embodiments, that iswearing the HWC. It should be understood that this terminology is tohelp the reader and make for clear presentations of the varioussituations and that other members of the Blueforce, or other people, mayhave HWC's 102 and have similar capabilities. In this embodiment, afirst person is wearing a head-worn computer 102 that has a see throughfield of view (“FOV”) 5914. The first person can see through the FOV toview the surrounding environment through the FOV and digital content canalso be presented in the FOV such that the first person can view theactual surroundings, through the FOV, in a digitally augmented view. Theother BlueForce person's location is known and is indicated at aposition inside of a building at point 5902. This location is known inthree dimensions, longitude, latitude and altitude, which may have beendetermined by GPS along with an altimeter associated with the otherBlueforce person. Similarly, the location of the first person wearingthe HWC 102 is also known, as indicated in FIG. 59 as point 5908. Inthis embodiment, the compass heading 5910 of the first person is alsoknown. With the compass heading 5910 known, the angle in which the firstperson is viewing the surroundings can be estimated. A virtual targetline between the location of the first person 5908 and the otherperson's location 5902 can be established in three dimensional space andemanating from the HWC 102 proximate the FOV 5914. The threedimensionally oriented virtual target line can then be used to presentenvironmentally position locked digital content in the FOV 5914, whichis indicative of the other person's location 5902. The environmentallyposition locked digital content 5902 can be positioned within the FOV5914 such that the first person, who is wearing the HWC 102, perceivesthe content 5902 as locked in position within the environment andmarking the location of the other person 5902.

The three dimensionally positioned virtual target line can berecalculated periodically (e.g. every millisecond, second, minute, etc.)to reposition the environmentally position locked content 5912 to remainin-line with the virtual target line. This can create the illusion thatthe content 5912 is staying positioned within the environment at a pointthat is associated with the other person's location 5902 independent ofthe location of the first person 5908 wearing the HWC 102 andindependent of the compass heading of the HWC 102.

In embodiments, the environmentally locked digital content 5912 may bepositioned with an object 5904 that is between the first person'slocation 5908 and the other person's location 5902. The virtual targetline may intersect the object 5904 before intersecting with the otherperson's location 5902. In embodiments, the environmentally lockeddigital content 5912 may be associated with the object intersectionpoint 5904. In embodiments, the intersecting object 5904 may beidentified by comparing the two person's locations 5902 and 5908 withobstructions identified on a map. In embodiments the intersecting object5904 may be identified by processing images captured from a camera, orother sensor, associated with the HWC 102. In embodiments, the digitalcontent 5912 has an appearance that is indicative of being at thelocation of the other person 5902, at the location of the intersectingobject 5904 to provide a more clear indication of the position of theother person's position 5902 in the FOV 5914.

FIG. 60 illustrates how and where digital content may be positionedwithin the FOV 6008 based on a virtual target line between the locationof the first person 5908, who's wearing the HWC 102, and the otherperson 5902. In addition to positioning the content in a position withinthe FOV 6008 that is in-line with the virtual target line, the digitalcontent may be presented such that it comes into focus by the firstperson when the first person focuses at a certain plane or distance inthe environment. Presented object A 6018 is digitally generated contentthat is presented as an image at content position A 6012. The position6012 is based on the virtual target line. The presented object A 6018 ispresented not only along the virtual target line but also at a focalplane B 6014 such that the content at position A 6012 in the FOV 6008comes into focus by the first person when the first person's eye 6002focuses at something in the surrounding environment at the focal plane B6014 distance. Setting the focal plane of the presented content providescontent that does not come into focus until the eye 6002 focuses at theset focal plane. In embodiments, this allows the content at position Ato be presented without when the HWC's compass is indicative of thefirst person looking in the direction of the other person 5902 but itwill only come into focus when the first person focuses on in thedirection of the other person 5902 and at the focal plane of the otherperson 5902.

Presented object B 6020 is aligned with a different virtual target linethen presented object A 6018. Presented object B 6020 is also presentedat content position B 6004 at a different focal plane than the contentposition A 6012. Presented content B 6020 is presented at a furtherfocal plane, which is indicative that the other person 5902 isphysically located at a further distance. If the focal planes aresufficiently different, the content at position A will come into focusat a different time than the content at position B because the two focalplanes require different focus from the eye 6002.

FIG. 61 illustrates several BlueForce members at locations with variouspoints of view from the first person's perspective. In embodiments, therelative positions, distances and obstacles may cause the digitalcontent indicative of the other person's location to be altered. Forexample, if the other person can be seen by the first person through thefirst person's FOV, the digital content may be locked at the location ofthe other person and the digital content may be of a type that indicatesthe other person's position is being actively marked and tracked. If theother person is in relatively close proximity, but cannot be seen by thefirst person, the digital content may be locked to an intersectingobject or area and the digital content may indicate that the actuallocation of the other person cannot be seen but the mark is generallytracking the other persons general position. If the other person is notwithin a pre-determined proximity or is otherwise more significantlyobscured from the first person's view, the digital content may generallyindicate a direction or area where the other person is located and thedigital content may indicate that the other person's location is notclosely identified or tracked by the digital content, but that the otherperson is in the general area.

Continuing to refer to FIG. 61, several BlueForce members are presentedat various positions within an area where the first person is located.The primary BlueForce member 6102 (also referred to generally as thefirst person, or the person wherein the HWC with the FOV for examplepurposes) can directly see the BlueForce member in the open field 6104.In embodiments, the digital content provided in the FOV of the primaryBlueForce member may be based on a virtual target line and virtuallylocked in an environment position that is indicative of the open fieldposition of the BlueForce member 6104. The digital content may alsoindicate that the location of the open field BlueForce member is markedand is being tracked. The digital content may change forms if theBlueForce member becomes obscured from the vision of the primaryBlueForce member or otherwise becomes unavailable for direct viewing.

BlueForce member 6108 is obscured from the primary BlueForce member's6102 view by an obstacle that is in close proximity to the obscuredmember 6108. As depicted, the obscured member 6108 is in a building butclose to one of the front walls. In this situation, the digital contentprovided in the FOV of the primary member 6102 may be indicative of thegeneral position of the obscured member 6108 and the digital content mayindicate that, while the other person's location is fairly well marked,it is obscured so it is not as precise as if the person was in directview. In addition, the digital content may be virtually positionallylocked to some feature on the outside of the building that the obscuredmember is in. This may make the environmental locking more stable andalso provide an indication that the location of the person is somewhatunknown.

BlueForce member 6110 is obscured by multiple obstacles. The member 6110is in a building and there is another building 6112 in between theprimary member 6102 and the obscured member 6110. In this situation, thedigital content in the FOV of the primary member will be spatially quiteshort of the actual obscured member and as such the digital content mayneed to be presented in a way that indicates that the obscured member6110 is in a general direction but that the digital marker is not areliable source of information for the particular location of obscuredmember 6110.

FIG. 62 illustrates yet another method for positioning digital contentwithin the FOV of a HWC where the digital content is intended toindicate a position of another person. This embodiment is similar to theembodiment described in connection with FIG. 62 herein. The mainadditional element in this embodiment is the additional step ofverifying the distance between the first person 5908, the one wearingthe HWC with the FOV digital content presentation of location, and theother person at location 5902. Here, the range finder may be included inthe HWC and measure a distance at an angle that is represented by thevirtual target line. In the event that the range finder finds an objectobstructing the path of the virtual target line, the digital contentpresentation in the FOV may indicate such (e.g. as described hereinelsewhere). In the event that the range finder confirms that there is aperson or object at the end of the prescribed distance and angle definedby the virtual target line, the digital content may represent that theproper location has been marked, as described herein elsewhere.

Another aspect of the present invention relates to predicting themovement of BlueForce members to maintain proper virtual marking of theBlueForce member locations. FIG. 63 illustrates a situation where theprimary BlueForce member 6302 is tracking the locations of the otherBlueForce members through an augmented environment using a HWC 102, asdescribed herein elsewhere (e.g. as described in connection with theabove figures). The primary BlueForce member 6302 may have knowledge ofthe tactical movement plan 6308. The tactical movement plan may bemaintained locally (e.g. on the HWCs 102 with sharing of the planbetween the BlueForce members) or remotely (e.g. on a server andcommunicated to the HWC's 102, or communicated to a subset of HWC's 102for HWC 102 sharing). In this case, the tactical plan involves theBlueForce group generally moving in the direction of the arrow 6308. Thetactical plan may influence the presentations of digital content in theFOV of the HWC 102 of the primary BlueForce member. For example, thetactical plan may assist in the prediction of the location of the otherBlueForce member and the virtual target line may be adjustedaccordingly. In embodiments, the area in the tactical movement plan maybe shaded or colored or otherwise marked with digital content in the FOVsuch that the primary BlueForce member can manage his activities withrespect to the tactical plan. For example, he may be made aware that oneor more BlueForce members are moving towards the tactical path 6308. Hemay also be made aware of movements in the tactical path that do notappear associated with BlueForce members.

FIG. 63 also illustrates that internal IMU sensors in the HWCs worn bythe BlueForce members may provide guidance on the movement of themembers 6304. This may be helpful in identifying when a GPS locationshould be updated and hence updating the position of the virtual markerin the FOV. This may also be helpful in assessing the validity of theGPS location. For example, if the GPS location has not updated but thereis significant IMU sensor activity, the system may call into questionthe accuracy of the identified location. The IMU information may also beuseful to help track the position of a member in the event the GPSinformation is unavailable. For example, dead reckoning may be used ifthe GPS signal is lost and the virtual marker in the FOV may indicateboth indicated movements of the team member and indicate that thelocation identification is not ideal. The current tactical plan 6308 maybe updated periodically and the updated plans may further refine what ispresented in the FOV of the HWC 102.

FIG. 64 illustrates a BlueForce tracking system in accordance with theprinciples of the present invention. In embodiments, the BlueForce HWC's102 may have directional antenna's that emit relatively low powerdirectional RF signals such that other BlueForce members within therange of the relatively low power signal can receive and assess itsdirection and/or distance based on the strength and varying strength ofthe signals. In embodiments, the tracking of such RF signals can be usedto alter the presentation of the virtual markers of persons locationswithin the FOV of HWC 102.

Another aspect of the present invention relates to monitoring the healthof BlueForce members. Each BlueForce member may be automaticallymonitored for health and stress events. For example, the members mayhave a watchband as described herein elsewhere or other wearablebiometric monitoring device and the device may continually monitor thebiometric information and predict health concerns or stress events. Asanother example, the eye imaging systems described herein elsewhere maybe used to monitor pupil dilatations as compared to normal conditions topredict head trauma. Each eye may be imaged to check for differences inpupil dilation for indications of head trauma. As another example, anIMU in the HWC 102 may monitor a person's walking gate looking forchanges in pattern, which may be an indication of head or other trauma.Biometric feedback from a member indicative of a health or stressconcern may be uploaded to a server for sharing with other members orthe information may be shared with local members, for example. Onceshared, the digital content in the FOF that indicates the location ofthe person having the health or stress event may include an indicationof the health event.

FIG. 65 illustrates a situation where the primary BlueForce member 6502is monitoring the location of the BlueForce member 6504 that has had aheath event and caused a health alert to be transmitted from the HWC102. As described herein elsewhere, the FOV of the HWC 102 of theprimary BlueForce member may include an indication of the location ofthe BlueForce member with the health concern 6504. The digital contentin the FOV may also include an indication of the health condition inassociation with the location indication. In embodiments, non-biometricsensors (e.g. IMU, camera, ranger finder, accelerometer, altimeter,etc.) may be used to provide health and/or situational conditions to theBlueForce team or other local or remote persons interested in theinformation. For example, if one of the BlueForce members is detected asquickly hitting the ground from a standing position an alter may be sentas an indication of a fall, the person is in trouble and had to dropdown, was shot, etc.

Another aspect of the present invention relates to virtually markingvarious prior acts and events. For example, as depicted in FIG. 66, thetechniques described herein elsewhere may be used to construct a virtualprior movement path 6604 of a BlueForce member. The virtual path may bedisplayed as digital content in the FOV of the primary BlueForce member6602 using methods described herein elsewhere. As the BlueForce membermoved along the path 6604 he may have virtually placed an event marker6608 such that when another member views the location the mark can bedisplayed as digital content. For example, the BlueForce member mayinspect and clear an area and then use an external user interface orgesture to indicate that the area has been cleared and then the locationwould be virtually marked and shared with BlueForce members. Then, whensomeone wants to understand if the location was inspected he can viewthe location's information. As indicated herein elsewhere, if thelocation is visible to the member, the digital content may be displayedin a way that indicates the specific location and if the location is notvisible from the person's perspective, the digital content may besomewhat different in that it may not specifically mark the location.

Turning back to optical configurations, another aspect of the presentinvention relates to an optical configuration that provides digitallydisplayed content to an eye of a person wearing a head-worn display(e.g. as used in a HWC 102) and allows the person to see through thedisplay such that the digital content is perceived by the person asaugmenting the see through view of the surrounding environment. Theoptical configuration may have a variable transmission optical elementthat is in-line with the person's see-through view such that thetransmission of the see-through view can be increased and decreased.This may be helpful in situations where a person wants or would bebetter served with a high transmission see-through view and when, in thesame HWC 102, the person wants or would be better served with lesssee-through transmission. The lower see-through transmission may be usedin bright conditions and/or in conditions where higher contrast for thedigitally presented content is desirable. The optical system may alsohave a camera that images the surrounding environment by receivingreflected light from the surrounding environment off of an opticalelement that is in-line with the person's see-through view of thesurrounding. In embodiments, the camera may further be aligned in a darklight trap such that light reflected and/or transmitted in the directionof the camera that is not captured by the camera is trapped to reducestray light.

In embodiments, a HWC 102 is provided that includes a camera that iscoaxially aligned with the direction that the user is looking. FIG. 67shows an illustration of an optical system 6715 that includes anabsorptive polarizer 6737 and a camera 6739. The image source 6710 caninclude light sources, displays and reflective surfaces as well as oneor more lenses 6720. Image light 6750 is provided by the image source6710 wherein, a portion of the image light 6750 is reflected toward theuser's eye 6730 by a partially reflective combiner 6735. At the sametime, a portion of the image light 6750 may be transmitted by thecombiner 6735 such that it is incident onto the absorptive polarizer6737. In this embodiment, the image light 6750 is polarized light withthe polarization state of the image light 6750 oriented relative to thetransmission axis of the absorptive polarizer 6737 such that theincident image light 6750 is absorbed by the absorptive polarizer 6737.In this way, faceglow produced by escaping image light 6750 is reduced.In embodiments, the absorptive polarizer 6737 includes an antireflectioncoating to reduce reflections from the surface of the absorptivepolarizer 6737.

FIG. 67 further shows a camera 6739 for capturing images of theenvironment in the direction that the user is looking. The camera 6739is positioned behind the absorptive polarizer 6737 and below thecombiner 6735 so that a portion of light from the environment 6770 isreflected by the combiner 6735 toward the camera 6739. Light from theenvironment 6770 can be unpolarized so that a portion of the light fromthe environment 6770 that is reflected by the combiner 6735 passesthrough the absorptive polarizer 6737 and it is this light that iscaptured by the camera 6739. As a result, the light captured by thecamera will have a polarization state that is opposite that of the imagelight 6750. In addition, the camera 6739 is aligned relative to thecombiner 6735 such that the field of view associated with the camera6739 is coaxial to the display field of view provided by image light6750. At the same time, a portion of scene light 6760 from theenvironment is transmitted by the combiner 6735 to provide a see-throughview of the environment to the user's eye 6730. Where the display fieldof view associated with the image light 6750 is typically coincident tothe see-through field of view associated with the scene light 6760 andthereby the see through field of view and the field of view of thecamera 6739 are at least partially coaxial. By attaching the camera 6739to the lower portion of the optical system 6715, the field of view ofthe camera 6739 as shown by the light from the environment 6770 moves asthe user moves their head so that images captured by the camera 6739correspond to the area of the environment that the user is looking at.By coaxially aligning the camera field of view with the displayed imageand the user's view of the scene, augmented reality images with improvedalignment to objects in the scene can be provided. This is because thecaptured images from the camera 6739 provide an accurate representationof the user's perspective view of the scene. As an example, when theuser sees an object in the scene as being located in the middle of thesee-through view of the HWC, the object will be located in the middle ofthe image captured by the camera and any augmented reality imagery thatis to be associated with the object can be located in the middle of thedisplayed image. As the user moves their head, the relative position ofthe object as seen in the see-through view of the scene will change andthe position of the augmented reality imagery can be changed within thedisplayed image in a corresponding manner. When a camera 6739 isprovided for each of the user's eyes, an accurate representation of the3D view of the scene can be provided as well. This is an importantadvantage provided by the invention because images captured by a cameralocated in the frame of the HWC (e.g. between the eyes or at thecorners) capture images that are laterally offset from the user'sperspective of the scene and as a result it is difficult to alignaugmented reality images with objects in the scene as seen from theuser's perspective.

In the optical system 6715 shown in FIG. 67, the absorptive polarizer6737 simultaneously functions as a light trap for escaping image light6750, a light blocker of the image light 6750 for the camera 6739 and awindow for light from the environment 6770 to the camera 6739. This ispossible because the polarization state of the image light 6750 isperpendicular to the transmission axis of the absorptive polarizer 6737while the light from the environment 6770 is unpolarized so that aportion of the light from the environment 6770 that is the oppositepolarization state to the image light is transmitted by the absorptivepolarizer 6737. The combiner 6735 can be any partially reflectivesurface including a simple partial mirror, a notch mirror and aholographic mirror. The reflectivity of the combiner 6735 can beselected to be greater than 50% (e.g. 55% reflectivity and 45%transmission over the visible wavelength spectral band) whereby amajority of the image light 6750 will be reflected toward the user's eye6730 and a majority of light from the environment 6770 will be reflectedtoward the camera 6739, this system will provide a brighter displayedimage, a brighter captured image with a dimmer see-through view of theenvironment. Alternatively, the reflectivity of the combiner 6735 can beselected to be less than 50% (e.g. 20% reflectivity and 80% transmissionover the visible wavelength spectral band) whereby the majority of theimage light 6750 will be transmitted by the combiner 6735 and a majorityof light from the environment 6770 will be transmitted to the user's eye6730, this system will provide a brighter see-through view of theenvironment, while providing a dimmer displayed image and a dimmercaptured image. As such, the system can be designed to favor theanticipated use by the user.

In embodiments, the combiner 6735 is planar with an optical flatnessthat is sufficient to enable a sharp displayed image and a sharpcaptured image, such as a flatness of less than 20 waves of light withinthe visible wavelengths. However, in embodiments, the combiner 6735 maybe curved in which case the displayed image and the captured image willboth be distorted and this distortion will have to be digitallycorrected by the associated image processing system. In the case of thedisplayed image, the image is digitally distorted by the imageprocessing system in a direction that is opposite to the distortion thatis caused by the curved combiner so the two distortions cancel oneanother and as a result the user sees an undistorted displayed image. Inthe case of the captured image, the captured image is digitallydistorted after capture to cancel out the distortion caused by thecurved combiner so that the image appears to be undistorted after imageprocessing.

In embodiments, the combiner 6735 is an adjustable partial mirror inwhich the reflectivity can be changed by the user or automatically tobetter function within different environmental conditions or differentuse cases. The adjustable partial mirror can be an electricallycontrollable mirror such as for example, the e-Transflector that can beobtained from Kent Optronics (http://www.kentoptronics.com/mirror.html)where the reflectivity can be adjusted based on an applied voltage. Theadjustable partial mirror can also be a fast switchable mirror (e.g. aswitching time of less than 0.03 seconds) wherein the perceivedtransparency is derived from the duty cycle of the mirror rapidlyswitching between a reflecting state and a transmitting state. Inembodiments, the images captured by the camera 6739 can be synchronizedto occur when the fast switchable mirror is in the reflecting state toprovide an increased amount of light to the camera 6739 during imagecapture. As such, an adjustable partial mirror allows for thetransmissivity of the partial mirror to be changed corresponding to theenvironmental conditions, e.g. the transmissivity can be low when theenvironment is bright and the transmissivity can be high when theenvironment is dim.

In a further embodiment, the combiner 6735 includes a hot mirror coatingon the side facing the camera 6739 wherein visible wavelength light issubstantially transmitted while a spectral wavelength band of infraredlight is substantially reflected and the camera 6739 captures imagesthat include at least a portion of the infrared wavelength light. Inthese embodiments, the image light 6750 includes visible wavelengthlight and a portion of the visible wavelength light is transmitted bythe combiner 6735, where it is then absorbed by the absorptive polarizer6737. A portion of the scene light 6760 is comprised of visiblewavelength light and this is also transmitted by the combiner 6735, toprovide the user with a see-through view of the environment. The lightfrom the environment 6770 is comprised of visible wavelength light andinfrared wavelength light. A portion of the visible wavelength lightalong with substantially all of the infrared wavelength light within thespectral wavelength band associated with the hot mirror, is reflected bythe combiner 6735 toward the camera 6739 thereby passing through theabsorptive polarizer 6737. In embodiments, the camera 6739 is selectedto include an image sensor that is sensitive to infrared wavelengths oflight and the absorptive polarizer 6737 is selected to substantiallytransmit infrared wavelengths of light of both polarization states (e.g.ITOS XP44 polarizer which transmits both polarization states of lightwith wavelengths above 750 nm: seehttp://www.itos.de/english/polarisatoren/linearlinear.php) so that anincreased % of infrared light is captured by the camera 6739. In theseembodiments, the absorptive polarizer 6737 functions as a light trap forthe escaping image light 6750 and thereby blocking the image light 6750that is in the visible wavelengths from the camera 6739 whilesimultaneously acting as a window for infrared wavelength light from theenvironment 6770 for the camera 6739.

By coaxially aligning the camera field of view with the displayed imageand the user's view of the scene, augmented reality images with improvedalignment to objects in the scene can be provided. This is because thecaptured images from the camera provide an accurate representation ofthe user's perspective view of the scene. In embodiments, the camerathat is coaxially aligned with the user's view captures an image of thescene, the processor then identifies an object in the captured image andidentifies a field of view position for the object, which can becompared to the displayed field of view correlated position so digitalcontent is then displayed relative to the position of the object.

Another aspect of the present invention relates to an optical assemblythat uses a reflective display where the reflective display isilluminated with a front light arranged to direct the illumination atangles around 90 degrees from the active reflective surface of thereflective display. In embodiments, the optical configuration is lightweight, small and produces a high quality image in a head-wornsee-through display.

FIG. 68 provides a cross sectional illustration of the compact opticaldisplay assembly for a HWC 102 according to principles of the presentinvention along with illustrative light rays to show how the lightpasses through the assembly. The display assembly is comprised of upperoptics and lower optics. The upper optics include a reflective imagesource 6810, a quarter wave film 6815, a field lens 6820, a reflectivepolarizer 6830 and a polarized light source 6850. The upper opticsconvert illumination light 6837 into image light 6835. The lower opticscomprise a beam splitter plate 6870 and a rotationally curved partialmirror 6860. The lower optics deliver the image light to a user who iswearing the HWC 102. The compact optical display assembly provides theuser with image light 6835 that conveys a displayed image along withscene light 6865 that provides a see-through view of the environment sothat user sees the displayed image overlaid onto the view of theenvironment.

In the upper optics, linearly polarized light is provided by thepolarized light source 6850. Where the polarized light source 6850 caninclude one or more lights such as LEDs, QLEDs, laser diodes,fluorescent lights, etc. The polarized light source 6850 can alsoinclude a backlight assembly with light scattering surfaces or diffusersto spread the light uniformly across the output area of the polarizedlight source. Light control films or light control structures can beincluded as well to control the distribution of the light (also known asthe cone angle) that is provided by the polarized light source 6850. Thelight control films can include, for example, diffusers, ellipticaldiffusers, prism films and lenticular lens arrays. The light controlstructures can include prism arrays, lenticular lenses, cylindricallenses, Fresnel lenses, refractive lenses, diffractive lenses or otherstructures that control the angular distribution of the illuminationlight 6837. The output surface of the polarized light source 6850 is apolarizer film to ensure that the illumination light 6837 provided tothe upper optics is linearly polarized.

The illumination light 6837 provided by the polarized light source 6850is reflected by a reflective polarizer 6830. Where the polarizer on theoutput surface of the polarized light source 6850 and the reflectivepolarizer 6830 are oriented so that their respective transmission axesare perpendicular to one another. As a result, the majority of theillumination light 6837 provided by the polarized light source 6850 isreflected by the reflective polarizer 6830. In addition, the reflectivepolarizer 6830 is angled so that the illumination light 6837 isreflected toward the reflective image source 6810 thereby illuminatingthe reflective image source 6810 as shown in FIG. 68.

The illumination light 6837 passes through a field lens 6820 and is thenincident onto the reflective image source 6810. The illumination light6837 is then reflected by the reflective image source (otherwisereferred to as a reflective display herein elsewhere) 6810. Wherein thereflective image source 6810 can comprise a liquid crystal on silicon(LCOS) display, a ferroelectric liquid crystal on silicon (FLCSO)display, a reflective liquid crystal display, a cholesteric liquidcrystal display, a bistable nematic liquid crystal display, or othersuch reflective display. The display can be a monochrome reflectivedisplay that is used with sequential red/green/blue illumination light6837 or a full color display that is used with white illumination light6837. The reflective image source 6810 locally changes the polarizationstate of the illumination light 6837 in correspondence to the pixel bypixel image content that is displayed by the reflective image source6810 thereby forming image light 6835. Wherein if the reflective imagesource 6810 is a normally white display, the areas of the image light6835 that correspond to bright areas of the image content end up with apolarization state that is opposite to the polarization state of theillumination light and dark areas of the image light 6835 end up with apolarization state that is the same as the illumination light 6837 (itshould be noted that the invention can be used with normally blackdisplays which provide an opposite effect on polarization in the imagelight). As such, the image light 6835 as initially reflected by thereflective image source 6810 has a mixed polarization state pixel bypixel. The image light 6835 then passes through the field lens 6820which modifies the distribution of the image light 6835 while preservingthe wavefront to match the requirements (such as for example,magnification and focus) of the lower optics. As the image light 6835passes through the reflective polarizer 6830, the bright areas of theimage light 6835 that have a polarization state that is opposite to theillumination light 6837 are transmitted through the reflective polarizer6830 and the dark areas of the image light 6835 that have the samepolarization state as the illumination light 6837 are reflected backtoward the polarized light source 6850, as a result, the image light6835 after passing through the reflective polarizer 6830 is linearlypolarized with a single polarization state in all the pixels of theimage but now with different intensities pixel by pixel. Thus thereflective polarizer 6830 acts first as a reflector for the illuminationlight 6837 and then second as an analyzer polarizer for the image light6835.

As such, the optical axis of the illumination light 6837 is coincidentwith the optical axis of the image light 6835 between the reflectivepolarizer 6830 and the reflective image source 6810. The illuminationlight 6837 and the image light 6835 both pass through the field lens6820, but in opposite directions. Wherein the field lens acts to expandthe illumination light 6837 so it illuminates the entire active area ofthe reflective image source 6810 and also to expand the image light 6835so it fills the eyebox 6882 after passing through the rest of thecompact optical display system. By overlapping the portion of thecompact optical display assembly associated with the illumination light6837 with the portion of the compact optical display assembly associatedwith the image light 6835, the overall size of the compact opticaldisplay assembly is reduced. Given that the focal length associated withthe field lens 6820 requires some space in the compact optical displayassembly, the reflective polarizer 6830 and the polarized light source6850 are located in space that would otherwise be unused so the overallsize of the display assembly is more compact.

The reflective polarizer 6830 can be a relatively thin film (e.g. 80microns) or thin plate (e.g. 0.2 mm) as shown in FIG. 68. The reflectivepolarizer 6830 can be a wiregrid polarizer such as is available fromAsahi Kasei under the name WGF, or a multilayer dielectric filmpolarizer such as is available from 3M under the name DBEF. Aspreviously described, the reflective polarizer 6830 has two functions.First, the reflective polarizer 6830 reflects the illumination light6837 provided by the polarized light source 6850 and redirects theillumination light 6837 toward the reflective image source 6810. Second,the reflective polarizer 6830 acts as an analyzer polarizer to the imagelight 6835 thereby converting the mixed polarization state of the imagelight 6835 above the reflective polarizer 6830 to linearly polarizedlight with a single polarization state below the reflective polarizer6830. While the illumination light 6837 incident on the reflectivepolarizer 6830 is incident on a relatively small portion of thereflective polarizer 6830, the image light 6835 is incident on themajority of the area of the reflective polarizer 6830. Consequently, thereflective polarizer 6830 extends at least across the entire area of thefield lens 6820 and may extend across the entire area between the fieldlens 6820 and the beam splitter 6870 as shown in FIG. 68. In addition,the reflective polarizer 6830 is angled at least in the portion wherethe illumination light 6837 is incident to redirect the illuminationlight 6837 toward the reflective image source 6810. However, sincereflective polarizers (such as a wiregrid polarizer) can be relativelyinsensitive to the incident angle, in a preferred embodiment, thereflective polarizer 6830 is a flat surface angled to redirect theillumination light 6837 toward the reflective image source 6810 whereinthe flat surface extends substantially across the entire area betweenthe field lens 6820 and the beam splitter 6870 in one continuously flatsurface to make manufacturing easier. The thin film or thin plate of thereflective polarizer 6870 can be retained at the edges to position it atthe desired angle and to make the surface flat.

The systems and methods described herein with respect to FIGS. 68through 71 have a number of advantages. By avoiding grazing angles ofthe illumination light 6837 and the image light 6835 at all the surfacesin the compact optical display assembly, scattering of light in theassembly is reduced and as a result the contrast of the image presentedto the user's eye 6880 is higher with blacker blacks. In addition, thereflective image source 6810 can include a compensating retarder film6815 as is known to those skilled in the art, to enable the reflectiveimage source 6810 to provide a higher contrast image with more uniformcontrast over the area of the displayed image. Further, by providing anoptical display assembly that is largely comprised of air, the weight ofthe compact optical display assembly is substantially reduced. By usingcoincident optical axes for the illumination light 6837 and the imagelight 6835 and overlapping the illumination light 6837 and image light6835 for a substantial portion of the optical display assembly, theoverall size of the compact optical display assembly is reduced. Wherethe coincident optical axes are provided by passing the illuminationlight 6837 and the image light 6835 in opposite directions through thefield lens 6820. To maintain a uniform polarization state for theillumination light 6837, the field lens 6820 is made from a lowbirefringence material such as glass or a plastic such as OKP4 asavailable from Osaka Gas Chemicals. By positioning the polarized lightsource 6850 and the associated illumination light 6837 below the fieldlens 6820, and by folding the optical path of both the illuminationlight 6837 at the reflective polarizer 6830 and the image light 6835 atthe beam splitter 6870, the overall height of the compact opticaldisplay assembly is greatly reduced. For example the overall height ofthe compact optical display assembly can be less than 24 mm as measuredfrom the reflective image source 6810 to the bottom edge of therotationally curved partial mirror 6860 for a display that provides a 30degree diagonal field of view with a 6×10 mm eyebox.

In a preferred case, the light control structure in the polarized lightsource 6850 includes a positive lens, such as for example a positiveFresnel lens, a positive diffractive lens or a positive refractive lens.Wherein a positive Fresnel lens or a positive diffractive lens ispreferred because they can be very thin. The illumination light 6837 isthereby focused to form a smaller area or pupil at the reflectivepolarizer 6830 that has a direct relationship to the area of an eyebox6882 at the other end of the optics wherein image light 6835 is providedto the user's eye 6880 as shown in FIG. 68. Where the positive lensconcentrates the illumination light 6837 from the polarized light source6850 both in terms of intensity and angular distribution to match theetendue of the optical system and thereby fills the eyebox with imagelight 6835. By using the positive lens to converge the light from thepolarized light source 6850 as provided to the reflective polarizer 6830and then using the field lens 6820 to expand the illumination light 6837to illuminate the active area of the reflective image source 6810,efficiency is improved since illumination light 6837 is substantiallydelivered only where needed to form image light 6835. Further,illumination light 6837 outside the pupil can be controlled by thepositive lens and clipped by masked edges of the positive lens. Byfocusing the illumination light 6837 and clipping light outside thepupil, illumination light 6837 is prevented from impinging adjacentsurfaces at grazing angles in the compact optical display assembly toreduce scattering of light and thereby increase contrast in the imageprovided to the user's eye 6830 by providing blacker blacks.

It should be noted that while FIGS. 68, 69 and 70 show optical layoutswherein the illumination light 6837 is provided from behind therotationally curved partial mirror 6860, other optical layouts arepossible within the invention. The location of the polarized lightsource 6850 can be changed for example to be at the side of therotationally curved partial mirror 6860 wherein the reflective polarizer6830 is oriented to receive the illumination light 6837 from the side.And reflect it toward the reflective image source 6810 (not shown).

In a further embodiment, the portion of the image light 6835 that isreflected back toward the polarized light source 6850 is recycled in thepolarized light source 6850 to increase the efficiency of the polarizedlight source 6850. In this case, a diffuser and a reflective surface isprovided behind the polarized light source 6850 so the polarization ofthe light is scrambled and reflected back toward the reflectivepolarizer 6830.

In yet another embodiment, another reflective polarizer is provided inthe polarized light source 6850 and behind the linear polarizerpreviously disclosed. Wherein the respective transmission axes of thereflective polarizer and the linear polarizer are parallel to oneanother. The other reflective polarizer then reflects the light backinto the backlight that has the polarization state that would not betransmitted by the linear polarizer. The light that is reflected backinto the backlight passes through diffusers associated with thepolarized light source 6850 where the polarization state is scrambledand reemitted thereby recycling the light and increasing efficiency.

In another embodiment, the system according to the principles of thepresent invention includes an eye imaging system. FIG. 69 is anillustration of a compact optical display assembly, which includes aneye imaging camera 6992 that captures an image of the user's eye 6880that is coaxial with the displayed image provided to the user so that afull image of the user's iris can be reliably captured. The eye imagingcamera 6992 is reflected into the lower optics by a reflective polarizer6930 that includes a notch mirror coating, facing the eye imaging camera6992, that reflects the wavelengths of light that are captured by theeye imaging camera 6992 (e.g. near infrared wavelengths) whiletransmitting wavelengths associated with the image light 6835 (e.g.visible wavelengths). Eye light rays 6995 shown in FIG. 69 illustratehow the field of view associated with the eye imaging camera 6992 is arelatively narrow field of view because it is multiply reflected throughthe lower optics to capture an image of the user's eye 6880. However, toenable the eye imaging camera 6992 to focus onto the user's eye 6880,the eye imaging camera 6992 needs to have a very near focus distance(e.g. 35 mm). In addition, the field of view and focus distance of theeye imaging camera must take into account the reducing effect of theoptical power provided by the rotationally curved partial mirror 6860.To increase the efficiency of capturing the light reflected from theuser's eye 6880 and thereby enable a brighter image of the eye, therotationally curved partial mirror 6860 can be coated with a partialmirror coating that acts as a full mirror in the wavelengths beingcaptured by the eye imaging camera 6992, for example the coating canreflect 50% of visible light associated with the image light and 90% ofnear infrared light associated with the eye light 6995. Where thereflections and associated changes in polarization state are similar tothose associated with the image light 6835 but in the opposite ordersince the eye light rays 6995 are coming from the user's eye 6880. LEDsor other miniature lights are provided adjacent to the user's eye 6880to illuminate the user's eye 6880 wherein the wavelengths associatedwith the LED's or other miniature lights are different than thewavelengths associated with the image light 6835 such as for examplenear infrared wavelengths (e.g. 850 nm, 940 nm or 1050 nm).Alternatively, the image light 6835 is used to illuminate the user's eye6880 and a reflective polarizer 6930 with a low extinction ratio inreflection (e.g. reflective extinction ratio <15) is used so that someof the eye light rays are reflected toward the eye imaging camera 6992.

In an alternative embodiment, the reflective and partially reflectivesurfaces can extend laterally to the sides of the areas used fordisplaying an image to the user. In this case, the eye imaging cameracan be located adjacent to the field lens and pointed in a direction toimage the user's eye after reflecting from the beam splitter and therotationally curved partial mirror as shown in FIG. 70. Where FIG. 70 isan illustration that shows an eye imaging camera 7092 positioned to theside of the field lens 6820 and reflective polarizer 6830. The eyeimaging camera 7092 is pointed such that the field of view captured bythe eye imaging camera 7092 includes the user's eye 6880 as illustratedby the eye light rays 7095. The quarter wave film 6890 is also extendedlaterally to change the polarization state of the eye light 7095 in thesame way that the polarization state of the image light is changed sothat the eye light passes through the beam splitter 6870 and quarterwave 6890, is partially reflected by the rotationally curved partialmirror 6860 and is then reflected by the beam splitter 6870 and is thencaptured by the eye imaging camera 7092. By positioning the eye imagingcamera 7092 to the side of the field lens 6820 and reflective polarizer6830, the complexity of the optics associated with displaying an imageto the user is reduced. In addition, the space available for the eyeimaging camera 7092 is increased since interferences with the displayoptics are reduced. By positioning the eye imaging camera 7092 adjacentto the display optics, the eye image is captured nearly coaxially withthe displayed image.

In a yet another embodiment, the systems according to the principles ofthe present invention include a field lens with an internal reflectivepolarizer and one or more surfaces with optical power. FIG. 71 is anillustration of the upper optics including a field lens 7121 comprisedof upper prism 7122 and lower prism 7123. The upper prism 7122 and thelower prism 7123 can be molded to shape or grind and polished. Areflective polarizer 7124 is interposed on the flat surface between theupper prism 7122 and the lower prism 7123. The reflective polarizer 7124can be a wiregrid polarizer film or a multilayer dielectric polarizer aspreviously mentioned. The reflective polarizer 7124 can be bonded intoplace with a transparent UV curable adhesive that has the samerefractive index as the upper prism 7122 or the lower prism 7123.Typically the upper prism 7122 and the lower prism 7123 would have thesame refractive index. Wherein upper prism 7122 includes an angledsurface for illumination light 6837 to be provided to illuminate thereflective image source 6810. The illumination light is provided by alight source that includes lights such as LEDs, a backlight 7151, adiffuser 7152 and a polarizer 7153 as has been previously described. Thelower prism 7123 includes a curved surface on the exit surface forcontrolling the wavefront of the image light 6835 as supplied to thelower optics. The upper prism may also include a curved surface on theupper surface next to the reflective image source 6810 as shown in FIG.71 for manipulating the chief ray angles of the light at the surface ofthe reflective image source 6810. Illumination light 6837 is polarizedby the polarizer 7153 prior to entering the upper prism 7122. Thetransmission axes of the polarizer 7153 and the reflective polarizer7124 are perpendicular to one another so that the illumination light6837 is reflected by the reflective polarizer 7124 so that theillumination light is redirected toward the reflective image source6810. The polarization state of the illumination light 6837 is thenchanged by the reflective image source 6810 in correspondence with theimage content to be displayed as previously described and the resultingimage light 6835 then passes through the reflective polarizer 7124 toform the bright and dark areas associated with the image that isdisplayed to the user's eye 6880.

In another embodiment, the field lens 7121 of FIG. 71 comprises apolarizing beam splitter cube including two prisms, upper prism 7122 andlower prism 7123. In this case, the reflective polarizer 7124 isreplaced by a coating that is polarization sensitive so that light ofone polarization state (typically S polarized light for example) isreflected and light of the other polarization state is transmitted. Theillumination light 6837 is then provided with the polarization statethat is reflected by the coating and the image light is provided withthe polarization state that is transmitted by the coating. As shown inFIG. 71, the beam splitter cube includes one or more curved surfaces inthe upper prism 7122 or the lower prism 7123. The beam splitter cube canalso include one or more angled surfaces where the illumination light issupplied. The angled surface can include light control structures suchas a microlens array to improve the uniformity of the illumination light6837, or a lenticular array to collimate the illumination light 6837.

In yet another embodiment, the curved surface(s) or the angledsurface(s) illustrated in FIG. 71 can be molded onto a rectangularlyshaped beam splitter cube by casting a UV curable material (e.g. UVcurable acrylic) onto a flat surface of a beam splitter cube, placing atransparent mold with a cavity that has the desired curve onto the flatsurface to force the UV curable material into the desired curve andapplying UV light to cure the UV curable material. The beam splittercube can be made of a material that has the same or different refractiveindex than the UV curable material.

In a further embodiment, polarization sensitive reflective coatings suchas dielectric partial mirror coatings, can be used in place ofreflective polarizers or beam splitters as shown in FIG. 68. In thiscase, the reflective films and plates that comprise the reflectivepolarizers 6830 and beam splitters 6870 include polarization sensitivecoatings that substantially reflect light with one polarization state(e.g. S polarization) while substantially transmitting light with theother polarization state (e.g. P polarization). Since the illuminationlight source includes a polarizer 7153, the illumination light 6837 isone polarization state and it is not important that the reflectivepolarizer 7124 be sensitive to the polarization state in reflection, thepolarization state just needs to be maintained and presented uniformlyover the surface of the reflective image source 6810. However, it isimportant that the reflective polarizer 7124 be highly sensitive topolarization state in transmission (e.g. extinction ratio >200) to be aneffective polarizer analyzer and to provide a high contrast image (e.g.contrast ratio >200) to the user's eye 6880.

In a further embodiment, the field lens 7121 shown in FIG. 71 cancomprise a reflective polarizer 7124 with a curved surface (not shown)instead of a flat surface and wherein the reflective polarizer 7124 isnot a film and instead is a polarization sensitive coating, a printedwiregrid polarizer or a molded wiregrid pattern that is then metallized.In this case, the upper prism 7122 and the lower prism 7123 are made asa matched pair with mating curved surfaces that together form thesurface of the reflective polarizer. Wherein the polarization sensitivecoating, the printed wiregrid or the molded wiregrid pattern are appliedto the mating curved surface associated either the upper prism 7122 orthe lower prism 7123 and a transparent adhesive is applied to the othermating surface to bond the upper prism 7122 and lower prism 7123together to form the field lens 7121 with an internal curved reflectivepolarizer 7121.

Another aspect of the present invention relates to manufacturing andproviding an optical element for use in a see-through computer displaysystem. In embodiments, a lightweight low-cost and high optical qualityoptical element.

In a head mounted display, a beam splitter can be used to directilluminating light from a light source toward a reflective image sourcesuch as an LCOS or a DLP. Where it is desirable to have a low weightbeam splitter with a flat partially reflective surface to provide goodimage quality. The flat partially reflective surface is particularlyimportant when an eye camera is provided for eye imaging that utilizesthe flat partially reflective surface for directing the field of view ofthe eye camera toward the user's eye.

Systems and methods provide for a lightweight beam splitter comprised ofmolded plastic elements and an internal plate element to provide a flatpartially reflective surface. Together the pieces form a triplet beamsplitter optic including two molded elements and a plate element. Byproviding the plate element internal to the beam splitter, the matchingsurfaces of the molded elements do not have to be optically flat,instead the plate element provides the flat surface and an indexmatching material is used to join the plate element to the moldedelements. All three elements can be plastic elements to reduce theweight and cost of the lightweight beam splitter. To provide a moreuniform refractive effect, the molded elements and the plate element arepreferentially made from plastic materials with similar refractive indexand have low birefringence.

FIG. 72 shows an illustration of the two molded elements 7210 and 7220.These molded elements are molded with a relatively uniform thickness toprovide uniform flow of the plastic material during molding (eitherinjection molding, compression molding or casting) and thereby enable alow birefringence in the elements as molded. To further reducebirefringence in the molded elements as molded, materials with lowviscosity and low stress optic coefficients are preferred including:OKP4 from Osaka Gas Company; Zeonex F52R, K26R or 350R from ZeonChemical; PanLite SP3810 from Teijin.

The molded elements 7210 and 7220 can include flat surfaces and surfaceswith optical power, where the surfaces with optical power can includespherical or aspheric curved surfaces, diffractive surfaces or Fresnelsurfaces. Flat surfaces, diffractive surfaces or Fresnel surfaces arepreferred on the surfaces associated with light that illuminates theimage source and flat surfaces, spherical surfaces or aspheric surfacesare preferred on the surfaces associated with image light. Moldedelement 7210 is shown with a spherical or aspheric surface 7215 andmolded element 7220 is shown with a flat surface 7225, however, any ofthe surfaces shown can be molded as flat surfaces or surfaces withoptical power.

After molding the molded elements 7210 and 7220 are machined to providematching angled surfaces. Molded element 7210 is shown in FIG. 73 wherea milling cutter 7328 is shown machining angled surface 7329. FIG. 74shows an illustration of molded elements 7210 and 7220 after they havebeen machined to respectively provide beam splitter elements 7430 and7440 that are prisms. The angled surface of beam splitter elements 7430and 7440 are machined to have matching angles. Alternatively, beamsplitter elements 7430 and 7440 can be machined from sheet material ormolded pucks. In either case of using machined angled surfaces or moldedangled surface in the beam splitter elements, the surfaces will not beoptically flat.

FIG. 75 shows an illustration of the assembled triplet beam splitteroptic, wherein the beam splitter elements 7430 and 7440 have beenassembled with a partially reflecting plate element 7560 to form a beamsplitter cube. Wherein the beam splitter elements 7430 and 7440 are madefrom either the same material or different materials that have a verysimilar refractive index (e.g. within 0.05 of each other). An indexmatching material is used at the interfaces between the beam splitterelements and the plate element. The index matching material can be afluid, a light curing adhesive, a moisture curing adhesive or athermally curing adhesive. The index matching material should have arefractive index that is very similar to that of the beam splitterelements (e.g. within 0.1).

The partially reflective plate element 7560 can be a transparent platewith a partially reflective layer that is either a partially reflectivecoating or a laminated partially reflective film. The transparent plateis preferably a cast sheet such as cell cast acrylic that has lowbirefringence, or a molded plaque of a low birefringence material suchas OKP4, Zeonex F52R, Zeonex K26R, Zeonex 350R or PanLite SP3810. Inaddition, the transparent plate should be optically flat (e.g. within 20microns over the surface and with a surface finish of less than 15nanometers), however optically flat surfaces are easily obtained insheet stock. By using an index matching material at the interfacesbetween the beam splitter elements 7430 and 7440 and the partiallyreflective plate element 7560, the lack of optical flatness of thesurface of the beam splitter elements 7430 and 7440 can be filled by theindex matching material so that the flatness of the reflective surfaceis determined by the flatness of the more easily obtained partiallyreflective plate element 7560 thereby providing a manufacturingadvantage. The partially reflective layer can be a partial mirror, areflective polarizer or a wiregrid polarizer where the reflectivepolarizer can be a coating or a film and the wiregrid polarizer can be afilm or a molded structure that is partially coated with a conductivelayer. Where a suitable reflective polarizer film can be obtained from3M available under the trade name of DBEFQ and a wiregird polarizer filmcan be obtained from Asahi-Kasei available under the trade name of WGF.In a preferred embodiment, the transparent plate of the partiallyreflective plate element 7560 has a refractive index that is verysimilar (e.g. within 0.1) to the refractive indices of the beam splitterelements 7430 and 7440

FIG. 76 shows an illustration of an optical system for a head mounteddisplay system. The system includes a reflective display as an imagesource 7667, a light source 7665 that can be a white light source or asequential color light source as appropriate for the image source 7665.Wherein the light source 7665 provides illumination light 7674 that canbe polarized light provided that a quarter wave layer is associated withthe image source 7667 or the partially reflecting plate element 7560 sothat the polarization of the illumination light 7674 is changed beforebecoming image light 7672. The illumination light 7674 is reflected by asurface of the partially reflecting plate element 7560, and thenreflected by the image source 7667, whereupon it passes through thepartially reflective plate element 7560 thereby becoming image light7672. The image light 7672 is then reflected by a partially reflectivecombiner 7682 so that the image light is directed toward the user's eye7680 to display an image to the user while simultaneously providing asee-through view of the environment. In the optical system, an indexmatching material can be used at the interface between the image source7665 and the beam splitter element 7440 so that the surface of the beamsplitter element 7440 does not have to be flat. It is contemplated bythe current inventions that the optical system may include additionallenses and other optical structures that are not shown to improve theimage quality or change the form factor of the optical system.

In another embodiment, beam splitter elements 7430 and 7440 are moldeddirectly to shape using injection molding or casting. The molded beamsplitter elements are then assembled as shown in FIG. 75 as describedpreviously herein.

In further embodiments, surfaces of the beam splitter elements aremolded or machined to have additional structures to provide furtherfeatures. FIG. 77 shows an illustration of lightweight beam splitter7750 that includes an extended partially reflective plate element 7760and an extended beam splitter element 7740, wherein the partiallyreflective surface is extended to provide additional area for theillumination light 7674 to be reflected toward the image source 7665.Where having an extended partially reflective surface is particularlyuseful when the image source 7665 is a DLP and the illumination light7665 must be delivered at an oblique angle. FIG. 78 shows a lightweightbeam splitter 7850 that includes an entrance surface 7840 for theillumination light 7674 that is angled so the illumination light 7674passes substantially perpendicularly through the entrance surface 7840.

In yet further embodiments, beam splitter element elements 7430 and 7440are machined from a single molded element. Where the single moldedelement is designed to provide the desired optical surfaces. Forexample, the molded element 7210 as shown in FIG. 72 has surfaces thatcould be used for both surface 7215 and 7225. A series of moldedelements 7210 could then be molded and some would be used to makemachined beam splitter elements 7430 and some for beam splitter elements7440. A partially reflective plate element 7560 would then be bondedwith the beam splitter element 7430 and 7440 using index-matchedadhesive as previously described herein. Alternatively, the singlemolded element 7210 could be designed with extra thickness across thedimension where the partially reflective plate element 7560 will beadded, so that a single molded element 7210 could be sawn, machined orlaser cut into beam splitter elements 7430 and 7440.

In another embodiment, a first molded optical element is molded in ageometry that enables improved optical characteristics including: lowbirefringence; more accurate replication of the optical surfaces of themold (reduced power and irregularity deviation). The first moldedoptical element is then cut to a different shape wherein the cuttingprocess leaves an optically rough surface finish. A second opticalelement with an optically smooth surface is then bonded to the opticallyrough surface of the first molded optical element using an index matchedadhesive to provide a combined optical element. The index matchedadhesive fills in the optically rough surface on the first moldedoptical element so that the optically rough surface is no longer visibleand an optically smooth surface is provided in the combined opticalelement by the second optical element. The optical characteristics ofthe combined optical element are improved as compared to a directlymolded optical element that has the geometry of the combined opticalelement. The cut surface can be flat or curved, as long as the cutsurface of the first molded optical element is substantially similar tothe bonding surface of the second optical element. In addition, both thefirst molded optical element and the second optical element can provideoptical surface with independent optical features such as optical power,wedge, diffraction, grating, dispersion, filtering and reflection. Forexample, optically flat surfaces can be difficult to mold on plasticlenses. A lens can be molded to provide a spherically curved surface andanother surface that is subsequently milled off to provide a flatsurface with a rough surface finish. An optically flat sheet can then bebonded to the milled surface using an index matched adhesive to providea combined optical element with an optically flat surface.

In yet further embodiments, surfaces of the beam splitter elementsinclude molded or machined structures to collimate, converge, diverge,diffuse, partially absorb, redirect or polarize the illumination light7674 or the image light 7672. In this way, the number of parts in thelightweight beam splitter is reduced and the cost and manufacturingcomplexity is reduced.

The multi-piece lightweight solid optic has been described in connectionwith certain embodiments; it should be understood that the multi-piecelightweight solid optic may be used in connection with other opticalarrangements (e.g. other see-through head-worn display opticalconfiguration described herein elsewhere).

In embodiments, the invention provides methods for aligning images,along with methods and apparatus for controlling light within the opticsof the display assembly associated with a HMD to prevent scattering andalso to trap excess light to thereby improve the image quality providedto the user.

FIG. 79a is a schematic illustration of a cross section of a displayassembly for a HMD. Wherein, the display assembly includes upper optics795 and lower optics 797 that operate together to display an image to auser while simultaneously providing a see-through view of theenvironment. Aspects of the upper optics 795 will be discussed in moredetail herein. The lower optics 797 can comprise optical elements tomanipulate image light 7940 from the upper optics 795 and therebypresent the image light 7940 to the user's eye 799. Lower optics 797 cancomprise one or more lenses 7950 and a combiner 793. The combiner 793presents the image light 7940 to the user's eye 799 while simultaneouslyallowing light from the environment 791 to pass through to the user'seye 799 so that the user sees the displayed image overlaid onto a viewof the environment.

FIG. 79 is a schematic drawing of a cross section of the upper optics795 for a HMD. Included are a light source 7910, a partially reflectivelayer 7930, a reflective image source 7935 and a lens 7950. The lightsource 7910 provides illumination light 7920 to the HMD. Theillumination light 7920 is redirected by the partially reflective layer7930 to illuminate the reflective image source 7935. The illuminationlight 7920 is then reflected by the reflective image source 7935 incorrespondence with the image content in the displayed image so that itpasses through the partially reflective layer 7930 and thereby formsimage light 7940. The image light 7940 is optically manipulated by thelens 7950 and other optical elements (not shown) in the lower optics 797so that a displayed image is provided to a user's eye 799. Together, thelight source 7910, the partially reflective layer 7930 and thereflective image source 7935 form a frontlighted image source. Where,the reflective image source 7935 can comprise a LCOS, a FLCOS, DLP orother reflective display. FIGS. 79, 80, 82 and 83 are shown with theillumination light 7920 provided so that it is incident on thereflective image source 7935 at an oblique angle as is required for aDLP. FIGS. 84c, 84d , 85, 86, 87, 88 and 89 are shown with theillumination light 7920 provided perpendicular to the reflective imagesource 8535 as is required for an LCOS or FLCOS. The principles of theinvention described herein apply to any type of reflective image sourcewhere stray reduction is needed. The light source 7910 can include lightsources such as LEDs, laser diodes or other light sources (e.g. asdescribed herein) along with various light control elements including:diffusers, prismatic films, lenticular films, Fresnel lenses, refractivelenses and polarizers. Polarizers included in the light source 7910polarize the light exiting the light source 7910 so that theillumination light 7920 is polarized. The partially reflective layer7930 can be a partial mirror coating on a substrate or it can be areflective polarizer film such as a wire grid film supplied byAsahi-Kasei under the name WGF or a multilayer polarizer film suppliedby 3M under the name DBEF. When the partially reflective layer 7930 is areflective polarizer, the illumination light 7920 is supplied aspolarized light wherein the polarization axis of the illumination light7920 is oriented relative to the polarization axis of the reflectivepolarizer so that the illumination light 7920 is substantiallyreflected. The reflective image source 7935 then includes a quarter waveretarder (e.g, a quarter wave film) so that the polarization state ofthe illumination light 7920 is reversed in the process of beingreflected by the reflective image source 79345. This enables thereflected illumination light 7920 to then be substantially transmittedby the reflective polarizer. After passing through the partiallyreflective layer 7930, the light becomes image light 7940. The imagelight 7940 then passes into a lens 7950 which is part of the loweroptics 797 or display optics which manipulates the light to provide adisplayed image to the user's eye. While the partially reflective layer7930 is illustrated as a flat surface, the inventors have contemplatedthat the surface may be curved, shaped, have simple or complex angles,etc. and such surface shapes are encompassed by the principles of thepresent invention.

In HMDs that provide images to both eyes of the user, it is desirable toprovide the images so that they are aligned to one another. This isparticularly important when the images are viewed as stereo images wherethe perceived alignment of the images seen with each eye is critical toachieving the perception of depth. To provide an accurate alignment ofthe images, an active alignment of the optics can be performed after theoptics have been assembled into a rigid frame of the HMD. Where activealignment includes aligning the images for each eye to one another bymoving portions of the display assembly and affixing the portions intoposition relative to one another. To this end, FIG. 79 shows space 7952that extends around the reflective image source 7935 so that thereflective image source 7935 can be moved laterally and rotationally.The light source 7910 and partially reflective layer 7930 are arrangedto illuminate the area that includes the reflective image source 7935and a portion of the adjacent space 7952. As a result, the reflectiveimage source 7935 can be moved within the space 7952 during the activealignment process without losing illumination or degrading thebrightness of the displayed image. Where movements of the reflectiveimage source 7935 during the active alignment can include movements thatcorrespond to horizontal, vertical and rotational movements of the imageprovided to one eye relative to the image provided to the other eye ofthe user. The movements can be 0.5 mm in size for example when thereflective image source 7935 is approximately 5×8.5 mm in size (thisequates to approximately 10% of the reflective image source dimension)and as such the space 7952 can be 0.5 mm wide or wider.

However, by including the space 7952, in the illuminated area, visibleartifacts can occur due to light scattering or reflecting from the edgesof the reflective image source 7935 or from structures adjacent to thespace 7952. Consequently, a mask 8055 is provided that extends from theedge of the active area of the reflective image source 7935 across thespace 7952 to cover the edges of the reflective image source 7935 andstructures adjacent to the space 7952 as shown in FIG. 80. The mask 8055is black and non-reflecting so that incident illumination light 7920 isabsorbed. In addition the mask 8055 is designed to not interfere withthe movements of the reflective image source 7935 that occur duringactive alignment. To this end, the mask 8055 can be stiff (e.g. a blackplastic or a black coated metal) and designed to slide under theadjacent structures such as the light source 7910, the edge of thepartially reflective layer 7930 and the sides of the housing thatcontain the frontlight. Alternatively, the mask 8055 can be flexible(e.g. a black plastic film or a black rubber film or tape) so that itdeforms when it contacts the adjacent structures. FIG. 81a shows anillustration of the reflective image source 7935, the light source 7910and the space 7952 as viewed from above. As is typically found withimage source of all kinds, there is a mask 8168 applied to the surfaceof the image source that surrounds the active area 8165, however thismask 8168 does not cover the space 7952. FIG. 81b shows a furtherillustration of the system shown in FIG. 81a wherein the mask 8055 isapplied to the reflective image source 7935 so that it attaches withinthe mask 8168 in a way that covers the space 7952 and does not block theactive area 8165.

In another embodiment, the image produced by the image source does notuse all of the active display area of the image source so there is roomto shift the image in an x and/or y perspective within the activedisplay area for alignment of the content. For example, if amisalignment is observed (as indicated above) rather than physicallymoving the image source, or in addition to moving the image source, theimage is digitally shifted in the x and/or y direction to create bettercombined content alignment. The originally inactive display area aroundthe content may be referred to as a content shift buffer zone.

In a further embodiment for aligning images in a HMD with see-through, afirst image containing features is provided to one eye of the user usinga display assembly similar to that shown in FIG. 79a or FIG. 85. Asecond image containing features in the same locations is provided tothe other eye of the user. The position of at least one of the imagesources is then moved within the space provided for adjustment to alignthe first image to the second image as seen by the user's eyes. Thisimage alignment can also be done using cameras in place of the user'seyes.

In the case where the first and second images are smaller in size thanthe active area of the reflective image source, thereby leaving adigital space adjacent to the images that can be used for digitalshifting of the images for further alignment adjustment. This adjustmentcan be used in combination with physical movements of the reflectiveimage sources to align the first image to the second image.

FIG. 82 is an illustration of upper optics 825 that includes theelements of upper optics 795 with the addition of a trim polarizer 8260.Where the polarization axis of the trim polarizer 8260 is oriented sothe image light 7940 is transmitted to the lower optics (not shown).Light that has the opposite polarization state compared to the imagelight 7940 is absorbed by the trim polarizer 8260. As such, light thatis scattered from surfaces such as the walls of the housing 8262 thattypically has a mixed polarization state will be partially absorbed bythe trim polarizer 8260. The trim polarizer 8260 can also absorb aportion of colored light caused by birefringence in the lens 7950provided the trim polarizer 8260 is located after the lens 7950. In thiscase, the trim polarizer 8260 absorbs the light that has the oppositepolarization state caused by the birefringence and transmits the lightthat has the polarization state of the image light 7940 prior to thelens 7950. In some cases, it is advantageous to change the polarizationstate of the image light 7940 to improve the reflection of the imagelight 7940 from the combiner 793 so that a half wave retarder is neededin addition to the trim polarizer 8260. For proper operation, the halfwave retarder is positioned with its fast axis oriented at 45 degrees tothe transmission axis of the trim polarizer 8260. In this case, it isadvantageous to position the half wave retarder (not shown) below thetrim polarizer 8260 so that the trim polarizer can absorb any ellipticalpolarization that may be present due to birefringence in the lens 7950before the image light is acted upon by the half wave retarder. In thisway, any variation in retardation with wavelength that may be present inthe half wave retarder will not act to increase the ellipticalpolarization or act to increase color artifacts in the image light 7940caused by birefringence in the lens 7950. In an example, the trimpolarizer can be a polarizer film that is laminated to a half waveretarder film and antireflection coatings can be applied to the outersurfaces.

In FIG. 83, the partially reflective layer 8330 is a laminated multiplepolarizer film comprised of a reflective polarizer film 8332 laminatedto an absorptive polarizer film 8331. Where, the reflective polarizerfilm 8332 is only big enough to reflect the illumination light 7920 thatilluminates the active area 8165 of the reflective image source 7935.The absorptive polarizer film 8331 is larger than the reflectivepolarizer film 8332 and extends across the entire aperture between thereflective image source 7935 and the lens 7950, so that no edges of theabsorptive polarizer film 8331 are visible and all the light reflectedfrom the reflective image source 7935 passes through the absorptivepolarizer 8331. For the case when the reflective image source 7935 is anLCOS, the absorptive polarizer 8331 acts as an analyzer polarizer toonly allow the polarization state of the image light to be transmitted.As such, the reflective polarizer film 8332 only covers a portion of theabsorptive polarizer film 8331. The polarization axes of the reflectivepolarizer film 8332 and the absorptive polarizer film 8331 are alignedso that polarized light that is transmitted by the reflective polarizerfilm 8332 is also transmitted by the absorptive polarizer film 8331. Incontrast, polarized light that is reflected by the reflective polarizerfilm 8332 is absorbed by the absorptive polarizer film 8331. Thereby,illumination light 7920 that is incident onto the reflective polarizerfilm 8332 is reflected toward the reflective image source 7935 where thepolarization state is reversed so that it is transmitted by thereflective polarizer film 8332 and the absorptive polarizer film 8331 asit becomes image light 7940. At the same time, illumination light 7920that is incident onto the absorptive polarizer film 8331 in the areasurrounding the reflective polarizer film 8332 is absorbed by theabsorptive polarizer film 8331. By absorbing this excess illuminationlight 7920, that would not illuminate the active area 8165 of thereflective image source 7935, stray light is reduced within the displayassembly and the contrast in the image presented to the user's eye isincreased as a result. By aligning the polarization axes of thereflective polarizer film 8332 and the absorptive polarizer film 8331,the transmission is only reduced by approximately 12%, in the regionsthat include both reflective polarizer film 8332 and absorptivepolarizer film 8331 compared to the regions that include just absorptivepolarizer film 8331. Given the location of the partially reflectivelayer 8330 in the optical system and the fact that it is remote from thereflective image source 7935, having local differences in transmissionon the partially reflective layer 8330 comprised of a laminated multiplepolarizer will have a very small effect on the brightness uniformity inthe image provided to the user's eye. In addition, the fact that thepartially reflective layer 8330 is remote from the reflective imagesource 8330 makes the edges of the reflective polarizer film 8332indistinct as seen by the user.

FIGS. 84a and 84b show illustrations of examples of partially reflectivelayers 8330, comprised of a reflective polarizer film 8430 and 8431laminated to an absorptive polarizer film 8432. The reflective polarizerfilms 8430 and 8431 are cut to a shape that covers only the area whereillumination light 7920 will be reflected to illuminate the active area8165 of the reflective image source 7935. The shape required for thereflective polarizer film will vary depending on the type of frontlight.For the frontlight shown in FIG. 83 where the partially reflective layer8330 is located adjacent to the reflective image source 7935, the shapeof the reflective polarizer film 8431 will be rectangular or oval suchas shown in FIG. 84b . For the frontlight included in the displayassembly shown in FIG. 85 where the lens 8550 is located between thepartially reflective layer 8530 and the reflective image source 8535,the influence of the illumination light 8520 passing through the lens8550 changes the distribution of illumination light 8520 needed from thelight source 8510. As a result, the illumination light 8520 can coveronly a portion of the partially reflective layer 8530 and the use of alaminated multiple polarizer is advantageous. In embodiments, thereflective polarizer film can cover less than 80% of the area of theabsorptive polarizer film in the laminated partially reflective layer.In further embodiments, the reflective polarizer film can cover lessthan 50% of the area of the absorptive polarizer film in the laminatedpartially reflective layer. In this case, the partially reflective layer8530 can include a reflective polarizer film 8430 with a shape similarto that shown in FIG. 84a . In any case, the shape of the reflectivepolarizer film is selected in concert with the optical elements in thefrontlight and display optics associated with the display assembly ofthe HMD.

FIG. 84c shows an example illustration of a frontlight for a displayassembly similar to that shown in FIG. 85 wherein a laminated multiplepolarizer film 8436 is shown with a complex curved shape that resemblesan S with a central flat portion and curved ends. The laminated multiplepolarizer 8436 includes a reflective polarizer film 8438 and anabsorptive polarizer film 8437. Illumination light 8520 includes rays8522 that are incident on the reflective polarizer film 8438 and rays8521 that are incident on the absorptive polarizer film 8437. Due to thealignment of the polarization of the illumination light 8520 to thepolarization axes of the reflective polarizer film 8438 and theabsorptive polarizer film 8437 as previously described herein, rays 8522are reflected by the reflective polarizer film 8438 and rays 8521 areabsorbed by the absorptive polarizer film 8437. In this way, rays 8521are prevented from contributing to stray light. It is beneficial toabsorb rays 8521 since they cannot contribute to image light 8540because if they were reflected by the laminated multiple polarizer 8436they would be incident on the reflective image source 8535 outside ofthe active area 8165, and if they were transmitted by the laminatedmultiple polarizer 8436, they would be incident on the housing sidewalls8262. Consequently, by absorbing rays 8521, the laminated multiplepolarizer 8436 reduces stray light and thereby increases the contrast inthe image displayed to the user.

FIG. 84d shows a further example illustration of a frontlight for adisplay assembly similar to that shown in FIG. 79 wherein the partiallyreflective layer 7930 comprises a laminated multiple polarizer film witha curved surface. The laminated polarizer includes an absorptivepolarizer film 8442 with a laminated reflective polarizer film 8441. Thereflective polarizer film 8441 is positioned in the central portion ofthe absorptive polarizer film 8442 where the illumination light 7920 isreflected toward the reflective image source 7935. The polarization axesof the reflective polarizer film 8441 and the absorptive polarizer film8442 are aligned in parallel to each other and perpendicular to thepolarization axis of the illumination light 7920 as provided by thepolarized light source 7910. The rays 8421 of the illumination light7920 that are incident on the partially reflective layer 7930 outside ofthe reflective polarizer film 8441 are absorbed by the absorptivepolarizer film 8442. The reflective light source 8535 includes a quarterwave layer 8443 so that the polarization axis of the illuminating light7920 is changed during the process of being reflected from thereflective image source 8535. As a result, the reflected illuminationlight 7920 is transmitted by the reflective polarizer film 8441 and theabsorptive polarizer film 8442, thereby becoming image light 7940. Byabsorbing the rays 8421, before they are incident on external surfacessuch housing walls or other optical surfaces, stray light is reduced andas a result the contrast in the image provided to the user's eye isincreased. It should be noted that while FIGS. 84c and 84d show thereflective polarizer film being positioned to reduce stray light fromthe left and right sides as shown in the figure, the reflectivepolarizer can similarly be positioned to reduce stray light in thedirection in and out of the paper as shown in the figure. FIGS. 84a and84b show reflective polarizer films 8430 and 8431 positioned in a centerportion of the absorptive polarizer 8432 so that stray light can bereduced in all directions. An important aspect of the invention is thatthis stray light reduction is obtained without a reduction in thebrightness of the image provided to the user's eye since the reflectivepolarizer films 8430 and 8431 reflect illumination light over the entirearea that is needed to fully illuminate the reflective image source.

FIG. 85 shows a schematic illustration of a display assembly for a HMDwherein the optical elements of the frontlight are overlapped with thedisplay optics, as the lens 8550 is located between the partiallyreflective layer 8530 and the reflective image source 8535. The displayassembly is then comprised of upper optics and lower optics. The upperoptics include a reflective image source 8535, a lens 8550, a partiallyreflective layer 8530 and a light source 8510. The upper optics convertillumination light 8520 into image light 8540. As shown, the loweroptics comprise a beam splitter plate 8580, a quarter wave film 8575 anda rotationally curved partial mirror 8570 (lower optics similar to thoseshown in FIG. 79a are also possible). The lower optics deliver the imagelight 8540 to a user's eye 8582. As previously stated herein, thedisplay assembly provides the user with image light 8540 that conveys adisplayed image along with scene light 8583 that provides a see-throughview of the environment so that the user sees the displayed imageoverlaid onto a view of the environment.

FIG. 85 shows a display assembly wherein the partially reflective layer8530 is a single flat film. However, it can be advantageous to use asegmented partially reflective layer 8630 such as is shown in FIG. 86.In this way, the angle of the central portion 8631 of the partiallyreflective layer 8630 can be selected to position the light source 8610differently to reduce the clipping of illumination light 8620 by thelens 8550 or other portions of the supporting structure associated withthe display assembly and thereby improve brightness uniformity in thedisplayed image seen by the user's eye 8582. To this end, a comparisonof FIG. 85 to FIG. 86 shows that by changing the angle of the centralportion of the partially reflective film, the position of the lightsource 8610 is moved downward and the clearance of the illuminationlight 8620 is increased relative to the lens 8550.

Segmented partially reflective layers can be used which a variety ofgeometries and makeups. FIG. 86 shows a segmented partially reflectivelayer 8630 that includes a folded Z shape with three flat sections. FIG.87 shows a segmented partially reflective layer that includes an S shapewith a central flat section 8731 and ends that are curved similar tothat shown in FIG. 84c . The segmented partially reflective layer cancomprise a single partially reflective layer such as a reflectivepolarizer film or a partial mirror film. In addition, illumination light8620 can be reflected from just the central flat section or it can bereflected from the central flat section plus one or more of the othersegments of the segmented partially reflective layer. Alternatively, thepartially reflective layer 8630 can comprise a multiple polarizer filmto selectively provide a partially reflective layer over just theportions of the partially reflective layer that are actually needed toreflect illumination light to uniformly illuminate the reflective imagesource 7935 as previously described herein. FIG. 88 shows a displayassembly wherein the partially reflective layer 8830 is comprised of alaminated multiple polarizer film with a central portion 8831 thatincludes a reflective polarizer film and the remainder of which is anabsorptive polarizer as previously described herein. Where the segmentedshape of the partially reflective layer 8830 is similar to that shown inFIG. 86. FIG. 89 shows a display assembly wherein the partiallyreflective layer 8930 is comprised of a laminated multiple polarizerfilm with a central portion 8931 that includes a reflective polarizerfilm and the remainder of which is an absorptive polarizer as previouslydescribed herein. Where the segmented shape of the partially reflectivelayer 8930 is similar to that shown in FIG. 87. While FIGS. 88 and 89show the reflective polarizer film as just occupying the flat centralsegment of the segmented partially reflective layers 8830 and 8930respectively, the reflective polarizer can extend into the adjacentsegments as needed to reflect the illumination light 8620 in the patternneeded to uniformly illuminate the reflective image source 8535.Alternatively the segments associated with the segmented partiallyreflective layers 8830 and 8930 can have three dimensional shapes whenthe reflective polarizer portion is shaped like that shown in FIG. 84ato keep the reflective polarizer 8430 portion flat.

In a further embodiment, the reflective polarizer film is laminated to aflexible transparent carrier film to increase the flexibility and theabsorptive polarizer film is a separate layer. FIG. 90 shows a partiallyreflective layer 9030 comprised of a reflective polarizer film 8441laminated to a flexible transparent carrier film 9043. Where theflexible transparent carrier film 9043 does not reflect the illuminationlight 7920 or change polarization state of the illumination light 7920and as a result rays 8421 pass through the flexible transparent carrierfilm 9043. The purpose of the flexible transparent carrier film is tosupport the reflective polarizer film 8441 while allowing the partiallyreflective layer 9030 to be substantially as flexible as the reflectivepolarizer film 8441 alone. Absorptive polarizer film 9042 is thenprovided as a separate layer positioned adjacent to the partiallyreflective layer 9030. While the absorptive polarizer film 9042 can beflat or curved as needed to fit within the available space, in apreferred embodiment, the absorptive polarizer film 9042 is curved to bebetter positioned to absorb rays 8421 that are incident on the partiallyreflective layer 9030 outside of the reflective polarizer film 8441 asshown in FIG. 90.

In yet another embodiment, the reflective polarizer film is modified tomake the portions transparent and non-reflective where illuminationlight is incident that is not needed to illuminate the active area ofthe reflective image source and a separate absorptive polarizer isprovided to absorb light that is transmitted through the non-reflectiveportions. FIG. 91 is an illustration of a partially reflective layer9130 comprised of a reflective polarizer film wherein portions 9143 aremodified to be transparent and non-reflective while the portion 9141 isa reflective polarizer. As such, polarized illumination light 7920 isreflected by the reflective polarizer portion 9141 and is transmitted bythe modified portions 9143. An absorptive polarizer 9042 is provided asa separate layer adjacent to the partially reflective layer 9130 so thatrays 8421 of the illumination light 7920 are transmitted by the modifiedportions 9143 and absorbed by absorptive polarizer. Wherein thetransmission axis of the reflective polarizer portion 9141 is parallelaligned to the transmission axis of the absorptive polarizer 9042. Themodification of the reflective polarizer film can be accomplished byetching the reflective polarizer film, when the reflective polarizerfilm is a wiregrid polarizer, and thereby removing the metal wires ofthe wiregrid in the modified portions. Alternatively the wiregridpolarizer can be masked during the metal deposition step to provideshaped portions of wire grid polarizer during manufacturing. Anadvantage provided by modifying the reflective polarizer film is thatthe flexibility of the partially reflective layer 9130 is substantiallyunchanged by the modification and as a result the partially reflectivelayer 9130 remains uniformly flexible in both the modified portions 9143and the reflective polarizer portion 9141. Another advantage provided byusing a modified reflective polarizer film is that the transition fromthe modified portion 9143 to the reflective polarizer portion 9141 doesnot include a sharp edge that can cause visible artifacts in the imageprovided to the user's eye due to scattering by the edge or a change inoptical density from a thickness change. This embodiment can also beapplied to other types of display assemblies such as for example thatshown in FIG. 85.

In a yet further embodiment, the partially reflective layer comprises areflective polarizer film laminated to an absorptive polarizer and thepartially reflective layer includes a flat portion and a curved portion.FIG. 92 is an illustration of a frontlight for a display assemblysimilar to that shown in FIG. 79a with the addition of a laminatedpartially reflective layer 9230 that has a portion that is a reflectivepolarizer laminated to an absorptive polarizer 9230. Where the partiallyreflective layer 9230 is segmented with a flat segment and a curvedsegment. By including a flat segment in the portion of the partiallyreflective layer 9230 that is a reflective polarizer 9241, theuniformity of illumination light 7920 that is reflected onto thereflective image source 7935 is improved because a larger portion of thelight source 7910 is mapped to the image as can be seen in FIG. 92.Wherein when using a small scale light source and associated lightcontrol films such as diffusers, it is important to map a large portionof the light source area to avoid darker or brighter lines across theimage produced by a dark or bright spot on the light source. Including aflat segment in the partially reflective layer 9230 also reduces localdistortions in the image provided to the user's eye that are caused bylocal changes in optical path length or localized refraction due tochanges in the surface angles that the light is exposed to. Thisembodiment can also be applied to other types of display assemblies suchas for example that shown in FIG. 85.

In head mounted displays that provide a displayed image overlaid onto asee-through view of the environment, it is advantageous to have highsee-through transmission both so the user can better interact with theenvironment and so that people in the environment can see the user'seyes so they feel more engaged with the user. It is also advantageous tohave a thin optics module with low height to make the head mounteddisplay more compact and thereby more attractive.

FIG. 93 shows an illustration of an optics module that provides the userwith a displayed image while simultaneously providing high see-thrutransmission. In this way, the user is provided with a displayed imageoverlaid onto a clear view of the environment. The optics moduleincludes a combiner 9320 that can have a partial mirror coating thattransmits a majority (greater than 50% transmission of visible light) ofthe available light from the environment, with transmission higher than70% preferred. For example, the combiner 9320 can have a broadbandpartial mirror that reflects less than 30% and transmits over 70% of theentire visible wavelength band. Alternatively, the combiner 9320 canhave a notch mirror coating where the reflectivity band of the notchmirror coating is matched to the wavelength bands provided by the lightsource 9340, where the light source 9340 can include one or more LEDs,QLEDs, diode lasers or other light source, each with narrow wavelengthbands (e.g. 50 nm wide bands or less, full width half max). The notchmirror coating can provide for example, greater than 20% reflectivity(e.g. 50% reflectivity) in the wavelengths bands provided by the lightsource 9340 while providing greater than 80% transmission in theremaining wavelength bands in the visible. For full color images to beprovided by the optics module, at least three LEDs with complimentarycolors are required such as red, green and blue light or, cyan, magentaand yellow light. In a preferred embodiment, the combiner 9320 has atristimulus notch mirror that reflects over 50% of the light within thewavelength bands provided by the light source 9340 and transmits anaverage of over 80% across the entire visible wavelength band. In thisway, the tristimulus notch mirror coating provides improved efficiencycompared to the partial mirror coating previously described. In anexample, if the combiner is to provide 75% transmission of visible lightfrom the environment 9362, the partial mirror coating will reflect only25% of image light 9360 so that 75% of the image light will betransmitted through the combiner and will not contribute to thebrightness of the image provided to the user's eye 9310. In contrast, atristimulus notch mirror coating can be used to reflect over 50% of theimage light 9360 over the wavelengths of light provided by the LEDs inthe light source 9340 while transmitting over 90% of the remainingwavelengths of visible light that are not provided by the LEDs so thatthe average transmission over the entire range of visible light is over75%. Consequently, the tristimulus notch mirror is twice as efficient asthe partial mirror in terms of the ability to reflect image light 9360toward the user's eye 9310.

To enable the optics module to operate with a combiner 9320 as shown inFIG. 93, image light 9360 is provided to a lens 9330 which focuses theimage light 9360 at the user's eye 9310. Wherein lens 9330 is shown as asingle lens element for simplicity, but multiple lens elements are alsopossible. The image light 9360 is provided from illumination light 9364that comes from the light source 9340. Where, the illumination light9364 is reflected by a beam splitter 9352 toward a reflective imagesource 9350. The image source 9350 can be a liquid crystal on silicondisplay (LCOS), a ferroelectric liquid crystal display (FLCOS) or othersuch reflective display. A polarizer 9342 can be associated with thelight source 9340 to provide polarized illumination light 9364. The beamsplitter 9352 can then be a reflective polarizer that is oriented tosubstantially reflect the polarized illumination light 9364. The imagesource 9350 changes the polarization state of the illumination light9364 when the light is reflected by the image source 9350 to form imagelight 9360 that has a polarization state that is opposite to that of theillumination light 9364. By changing the polarization state of theillumination light 9364 to the polarization state of the image light9360, the image light 9360 can then be transmitted by the reflectivepolarizer of the beam splitter 9352. It is important to note that theimage light 9360 is polarized to enable a folded illumination system andnot because polarized light is required by the combiner 9320. In fact,to provide a transmission of light from the environment 9362 that isgreater than 50%, the combiner 9320 cannot include a polarizer.

FIG. 94 is an illustration of an optics module than includes multiplyfolded optics to reduce the overall height of the optics module. In thiscase, illumination light 9464 is transmitted by the beam splitter 9452so that it passes directly toward the image source 9450 wherein the beamsplitter 9452 is a reflective polarizer and the light source 9340includes a polarizer 9342 that is oriented so the transmission axis ofthe polarizer 9342 is parallel to the transmission axis of the beamsplitter 9452. The illumination light 9464 is then reflected and changedin polarization state by the image source 9450 so that the image light9360 with its changed polarization state is reflected by beam splitter9452 toward the lens 9330. As can be seen by comparing FIG. 93 to FIG.94, the overall height of the optics module shown in FIG. 94 issubstantially reduced.

However, the orientation of the additional fold in the optical path ofthe image light 9360 in the optics module of FIG. 94 increases thethickness of the optics module, where thickness is defined as thedistance from the closest back surface of the optics module that isnearest to the user's eye to the farthest front surface of the opticsmodule that is farthest from the user's eye. FIGS. 95 and 96 showillustrations of an optical module where the added fold in the opticalpath of the image light 9360 is oriented perpendicular to the fold shownin FIG. 94. In this case, the optics module in FIGS. 95 and 96 is widerbut thinner than that shown in FIG. 94. FIG. 95 shows the optics modulefrom the side and FIG. 96 shows the optics module from the position ofthe user's eye 9310. As such, in the multiply folded optics shown inFIGS. 95 and 96, optical axis 935 associated with the illumination light9464 is perpendicular to both the optical axis 934 associated with theimage light 9360 as it passes through the lens 9330 and the optical axis933 associated with the image light 9360 as it proceeds toward theuser's eye 9310 in the eyebox. In the case of a head mounted display, itcan be very important to have a thin optics module because a thickoptics module can cause the head mounted display to stick outward fromthe user's forehead, which can be uncomfortable and unattractive. Thus,the multiply folded optics module shown in FIGS. 95 and 96 are shorterand thinner than the optic module shown in FIG. 93. The optics moduleshown in FIGS. 95 and 96 is wider than the optics module shown in FIG.93, but in a glasses configuration of the head mounted display, wideroptics modules can be better fit into the glasses frames than taller orthicker optics modules.

A further advantage that is provided by an optics module that includesmultiply folded optics is that twists can be introduced at the foldsurfaces to modify the orientation of different portions of the opticsmodule relative to each other. This can be important when the opticsmodule needs to fit into a thin curved glasses frame, a visor or ahelmet where the increased width associated with the upper portion ofthe multiply folded optics module can make it more difficult to fit intostructures that are not parallel to the combiner. In this case, theupper portion including for example (based on FIG. 96), the light source9340, the polarizer 9342, the beam splitter 9452 and the image source9450, can be twisted relative to the lower portion including the lens9330 and the combiner 9320. Where to avoid distortion of the image dueto the compound angles between the fold surfaces, a twist of the upperportion about the axis 934 must be combined with a corresponding twistof the lower portion about the axis 933. In this way, the effects of theincreased width of the upper portion of the multiply folded optics canbe reduced when fitting the optics module into a curved structure suchas glasses frames, a visor frame or a helmet structure.

FIG. 99 shows a further embodiment wherein the lens 9930 includes adiffractive surface 9931 to enable a more compact and shorter opticaldesign with reduced chromatic aberration. Where the diffractive surface9931 can be comprised of a series of small annular sections of arefractive lens curve such as for example in a Fresnel lens. Thediffractive surface 9931 can be flat as shown in FIG. 99 or it can havea base curve to provide additional optical power. The diffractivesurface 9931 can be a single order diffractive or a multiple orderdiffractive. To reduce scattering of wide angle illumination light 9964that could be incident on the diffractive surface 9931, an absorptivepolarizer 9932 is provided and is oriented with its transmission axisperpendicular to the transmission axis of the reflective polarizer ofthe beam splitter 9452. In this way, illumination light 9964 that istransmitted by the beam splitter 9452 in the direction that would causeit to be incident on the diffractive surface 9931 is absorbed by theabsorptive polarizer 9932 before it can be scattered by the diffractivesurface 9931. At the same time, image light 9360 has a polarizationstate that is opposite to that of the illumination light 9964 so that itis reflected by the beam splitter 9452 and transmitted by the absorptivepolarizer 9932 as it passes into the lens 9930.

FIG. 100 shows an illustration of an optics module that includes areduced angle between the beam splitter 9452 and the lens 9930 to reducethe overall height of the optics module. The fold angle of the imagelight 9360 (the deflection angle between 934 and 1005) is then more than90 degrees and as a result, the upper edge of the beam splitter iscloser to the lens 9330 thereby providing a reduced overall height ofthe optics module.

FIG. 100 also shows a compact planar light source 10040 comprised of athin edge-lit backlight similar to what is provided in displays used indisplays for mobile devices like cellphones. The compact planar lightsource 10040 is positioned directly behind the beam splitter 9452 toreduce the overall size of the optics module. The compact planar lightsource can include a light guide film or light guide plate with an edgelit light such as one or more LEDs and a reflector on the side oppositethe beam splitter 9452. The compact planar light source can include apolarizer so the illumination light 10064 is polarized as previouslydescribed herein. To direct the illumination light 10064 toward theimage source 9450 for improved efficiency, a turning film 10043 ispositioned between the compact planar light source 10040 and the beamsplitter 9452. A 20 degree prismatic turning film can be obtained forexample, from Luminit 103C (Torrance, Calif.) under the name DTF. Toobtain greater degrees of turning, such as 40 degrees, multiple layersof turning film 10043 can be stacked together provided they are orientedsuch that the turning effect is additive. A diffuser layer (not shown)can be used in addition to the turning film 10043 to reduce artifactssuch as linear shadows that can be associated with prismatic structuresthat are typically associated with turning films 10043. FIG. 101 showsan illustration of an optics module as seen from the position of theuser's eye, which is similar to that shown in FIG. 100 but with aperpendicular orientation of the added fold in the image light 10164 toreduce the thickness of the optics module as previously describedherein. As in the optics module shown in FIGS. 95 and 96, the multiplyfolded optics shown in FIG. 101 have an optical axis 1005 associatedwith the illumination light 10164 that is perpendicular to both theoptical axis 934 associated with the image light 9360 as it passesthrough the lens 9330 and the optical axis 933 associated with the imagelight 9360 as it proceeds toward the user's eye 9310 in the eyebox. As aresult, the optics module of FIG. 101 is thinner and shorter than theoptics module of FIG. 93. FIG. 101 also includes a field lens 10130 toimprove the optical performance of the optics module. The addition ofthis second lens element is possible because of the change in foldorientation so that the field lens 10130 does not increase the thicknessof the optics module, instead the added length of the optical path fromthe field lens 10130 occurs in the width of the optics module wherespace is more readily available in the head mounted display.

FIG. 102 shows an illustration of an optics module similar to that shownin FIG. 99 but with a different orientation of the upper portion of theoptics module relative to the combiner so that the combiner 10220 can bemore vertical. This rearrangement of the elements within the opticsmodule can be important to achieve a good fit of the head mounteddisplay onto the user's face. By making the combiner 10220 morevertical, the optics module can be made to have less interference withthe user's cheekbones.

FIGS. 103, 103 a and 103 b show illustrations of optics modules as seenfrom the position of the user's eye, that include multiply folded opticsand digital light projector (DLP) image sources 10350. In this case, theillumination light 10364 is provided at an oblique angle to the imagesource 10350 as required by the micromirrors in the DLP, to reflectimage light 9360 along the optical axis 934 of the lens 9930. Where, inthe case of a DLP image source 10350, image light 9360 is comprised ofon-state light reflected by on-state micromirrors in the DLP imagesource 10350 along optical axis 934, in correspondence to the brightnessof pixels in the image to be displayed to the user's eye 9310 in theeyebox. The micromirrors in the DLP image source 10350 also reflectoff-state light 10371 to the side of the optics module in correspondenceto the dark image content and as a result, a light trap 10372 isprovided in the optics module to absorb light 10371. The light trap10372 can be a black absorptive surface or a textured black surface. Thepurpose of the light trap 10372 is to absorb incident light 10371 andthereby reduce stray light and subsequently improve the contrast of theimage displayed to the user's eye 9310. As previously described in otherembodiments herein, the light source 10340 is provided to the side ofthe optics module with a multiply folded optical path to reduce theoverall thickness and height of the optics module. FIG. 103 provides theDLP image source 10350 at the top of the optics module so that the imagelight 9360 proceeds straight along the optical axis 934, through thelens 9930 and down to the combiner 9320 where the image light isreflected toward the user's eye 9310 located in the eyebox. A polarizer10341 is provided with the light source 10340 so that polarizedillumination light 10364 is reflected by the beam splitter 9452 toilluminate the DLP image source 10350. Where, the beam splitter 9452 inthis case, is a reflective polarizer that is aligned with the polarizer10341 so that the polarized illumination light 10364 is reflected by thebeam splitter 9452 and image light 9360 is transmitted by the beamsplitter 9452. A quarter wave film 10351 is located adjacent to thesurface of the DLP image source 10350 so that the polarization state ofthe image light 9360 is opposite to that of the illumination light 10364after being reflected by the DLP image source 10350. The light source10340 and the reflective polarizer 9452 are angularly arranged so thatthe illumination light 10364 is incident onto the DLP image source 10350at the oblique angle required so that the image light 9360 whenreflected by the on-state pixels in the DLP image source 10350 proceedsalong the optical axis 934 of the lens 9930. A field lens (similar to10130 as shown in FIG. 101) or other lens elements may be included inthe optics of FIG. 103 but is not shown, in which case, the illuminationlight 10364 and the image light 9360 may pass thru the field lens orother lens elements in opposite directions.

FIG. 103a is an illustration of another optics module with a multiplyfolded optical path that includes a DLP image source 10350 and is shownfrom the position of the user's eye. The light source 10340 is againprovided to the side of the optics module to reduce the thickness of theoptics module. In this case, the light source 10340 is provided on thesame side of the lens 9930 and combiner 9320, as the DLP image source10350. Lens 9930 can optionally include one or more diffractive surfaces9931. The light source 10340 directly illuminates the DLP image source10350 where the illumination light 10364 is incident on the DLP imagesource 10350 at an oblique angle so that the image light 9360, afterbeing reflected by the on-state micromirrors in the DLP image source10350, proceeds along the folded optical axis 934. At least one lighttrap 10372 is also provided to absorb light 10371 that is reflected fromoff-state micromirrors in the DLP and thereby improve the contrast ofthe displayed image as seen by the user. A field lens 10332 is providedbetween the DLP image source 10350 and the fold mirror 10352. Theillumination light L64 in this case can be unpolarized light whereuponthe fold mirror 10352 can be comprised of a full mirror coating (e.g. acoating that reflects the entire visible light spectrum) on a substrate.The field lens 10332 can be a single lens element as shown in FIG. 103aor it can include multiple lens elements as needed. The field lens 10332is designed to provide a large air gap between the field lens 10352 andthe DLP image source 10350, so that the illumination light 10364 can beintroduced to the optics module to directly illuminate the active areaassociated with the DLP image source 10350. By using unpolarizedillumination light 10364, the optics module shown in FIG. 103a hasimproved efficiency over the optics module with DLP image sources 10350shown in FIGS. 103 and 103 b.

FIG. 103b is an illustration of another optics module with multiplyfolded optical path that includes a DLP image source 10350 and is shownfrom the position of the user's eye 9310 in the eyebox. As in the opticsmodules shown in FIGS. 103 and 103 a, the optics module of FIG. 103b hasthe light source 10340 positioned at the side of the optics module toreduce the height and thickness of the optics module. The DLP imagesource 10350 is positioned opposite the light source 10340 however inthis embodiment they do not share an optical axis. The illuminationlight 10364 passes through the beam splitter 10352, which in this casecan be a first reflective polarizer. A second reflective polarizer 10332is positioned adjacent to the lens 9930 so that the illumination light10364 is reflected toward the DLP image source 10350. To reflect theillumination light 10364, the first reflective polarizer (beam splitter10352) and the second reflective polarizer 10332 are oriented withperpendicular transmission axes. A quarter wave film 10351 (or quarterwave coating on the DLP cover glass) is provided adjacent to the DLPimage source 10350 so that the polarization state of the illuminationlight 10364 is changed upon reflection from the DLP image source 10350as it becomes image light 9360. As a result, the polarization of theillumination light 10364 is opposite to that of the image light 9360.Consequently, the illumination light 10364 is transmitted by the beamsplitter 10352 and reflected by the second reflective polarizer 10332,while the image light 9360 is reflected by the beam splitter 10352 andtransmitted by the second reflective polarizer 10332. The light source10340 is oriented relative to the second reflective polarizer 10332 sothat it is reflected at an oblique angle relative to the DLP imagesource 10350 as required to provide image light 9360 reflected fromon-state micromirrors in the DLP image source 10350 along the foldedoptical axis 934. The second reflective polarizer 10332 can be extendedbeyond the lens 9930 to provide the required oblique angle to fullyilluminate the DLP image source 10350 as shown in FIG. 103b . Becausethe light source 10340 is located behind the beam splitter 10352, whichis a reflective polarizer, the light source 10340 does not affect theimage light 9360 and as a result, the light source 10340 can be adifferent size and orientation than the beam splitter 10352. One or morelight traps 10372 are provided to absorb light 10371 that is reflectedfrom off-state micromirrors in the DLP image source 10350 and therebyimprove the contrast of the displayed image. In this case, the lighttrap 10372 can be positioned under the second reflective polarizer 10332because the polarization state of the light 10371 is such that it isreflected by the beam splitter 10352 and transmitted by the secondreflective polarizer 10332. The combined orientation of the light source10340, the beam splitter 10352 and the DLP image source 10350 providesan optics module that is relatively thin and relatively short comparedto optics modules where the image source or the light source arepositioned above the fold mirror or beam splitter (e.g. such as theoptics module shown in FIG. 103).

FIGS. 97 and 98 show illustrations of optics modules similar to thoseshown in FIG. 94 but with the addition of an eye imaging camera 979 forcapturing images of the user's eye 9310 during use. In these cases, thelight source 9340 and image source 9450 are positioned opposite oneanother so that the eye imaging camera 979 can be positioned directlyabove the lens 9340 so that the optical axis 934 is shared between theoptics module and the eye imaging camera 979. By sharing a commonoptical axis, the eye imaging camera 979 can capture an image of theuser's eye 9310 that has a perspective from directly in front of theuser's eye 9310. Image light 9360 can then be used to illuminate theuser's eye 9310 during image capture. A portion of the light reflectedfrom the user's eye 9310, which can be unpolarized, passes through thebeam splitter 9452 before being captured by the eye imaging camera 979.Because the eye imaging camera 979 is located above the beam splitter9452, if the beam splitter 9452 is a reflective polarizer, thepolarization state of the image light 9360 will be opposite to that ofthe light 978 captured by the eye imaging camera 979. The eye imagingcamera 979 can be used to capture still images or video. Where videoimages can be used to track movements of the user's eye when looking atdisplayed images or when looking at a see-through view of theenvironment. Still images can be used to capture images of the user'seye 9310 for the purpose of identifying the user based on patterns onthe iris. Given the small size of available camera modules, an eyeimaging camera 979 can be added to the optics module with little impacton the overall size of the optics module. Additional lighting can beprovided adjacent to the combiner 9320 to illuminate the user's eye. Theadditional lighting can be infrared, so the user can simultaneously viewimages displayed with visible light. If the additional lighting isinfrared, the eye camera 979 must be capable of capturing images atmatching infrared wavelengths. By capturing images of the user's eyefrom the perspective of directly in front of the user's eye, undistortedimages of the user's eye can be obtained over a wide range of eyemovement.

FIG. 120 shows an illustration of another embodiment of an eye imagingcamera associated with the optics module shown in FIG. 101, however theeye imaging camera can be similarly included in optics modules such asthose shown in FIGS. 99, 100, 103, 103 b. These optics modules includeabsorptive polarizers 9932 to reduce stray light as previously disclosedherein. These optics modules can also include a diffractive surface9931, but the diffractive surface 9931 is not required for the operationof the eye imaging camera 979. In this embodiment, the polarizationstate of the image light 9360 is the same as that of the light that isreflected by the user's eye and captured by the eye imaging camera 979since they both pass through the absorptive polarizer 9932. In thisembodiment, the eye imaging camera 979 is positioned adjacent to thebeam splitter 9452 and the compact planar light source 10040 and betweenthe beam splitter and the field lens 10130. The optical axis 12034 ofthe light reflected by the eye is then angled somewhat relative to theoptical axis 934 of the image light 9360, so that the center of theuser's eye 9310 and the associated eyebox are within the field of viewof the eye imaging camera 979. In this way, the eye imaging camera 979captures images of the user's eye from nearly directly in front and onlyslightly to the side of the user's eye 9310 as shown in FIG. 120. WhileFIG. 120 shows the eye imaging camera 979 positioned adjacent to an endof the beam splitter 9452, it is also possible to position the eyeimaging camera 979 adjacent to a side of the beam splitter 9452. Theadvantage of this embodiment is that the eye imaging camera 979 isprovided with a simple optical path so that high image quality ispossible in the captured images of the user's eye 9310. It should benoted that the optics associated with the eye imaging camera must takeinto account the effect of the lens 9930 since the light reflected bythe user's eye 9310 that is captured by the eye imaging camera passesthrough the lens 9930. Also, the addition of the eye imaging camera 979does not substantially increase the volume of the optics module as canbe seen by comparing FIG. 120 to FIG. 101.

FIG. 121 shows an illustration of a further embodiment of an opticsmodule that includes an eye imaging camera 979. Similar to theembodiment shown in FIG. 120, this optics module also includes anabsorptive polarizer 9932 to reduce stray light and a diffractivesurface 9931 may be included, but is not required. In this embodiment,the eye imaging camera 979 is positioned between the beam splitter 9452and the field lens 10130 and pointed towards the beam splitter 9452. Inthis way, light reflected by the user's eye 9310 is reflected upwards bythe combiner 9320, passes through the lens 9930 and the absorptivepolarizer 9932 and then is reflected laterally toward the eye imagingcamera 979 by the beam splitter 9452. The light captured by the eyeimaging camera 979 is thereby the same polarization state as the imagelight 9360, so that it is reflected by the beam splitter 9452 andtransmitted by the absorptive polarizer 9932. The light reflected by theuser's eye 9310 can be unpolarized as initially reflected by the user'seye 9310, however, after passing through the absorptive polarizer 9932,the light becomes polarized with the same polarization state as theimage light 9360. An advantage of this embodiment is that it is evenmore compact than the embodiment shown in FIG. 120. This arrangement ofthe eye imaging camera 979 is also possible in the optics modules shownin FIGS. 99, 100, 103, 103 a and 103 b.

In the embodiments shown in FIGS. 120 and 121, the user's eye 9310 andthe associated eyebox can be illuminated by image light 9360 or anadditional light source can be provided for example, by an LEDpositioned adjacent to the combiner 9320. Where the LED can providevisible light or infrared light, provided the eye imaging camera cancapture at least a portion of the wavelengths of light provided by theLED.

In an alternative embodiment for the optics module shown in FIG. 103a ,the light source 10340 provides polarized illumination light 10364 andthe fold mirror 10352 is a reflective polarizer plate so that an eyecamera (not shown) can be positioned above the fold mirror 10352 andalong the optical axis 934 for capturing images of the user's eye 9310similar to that shown in FIGS. 97 and 98. The eye camera and the opticsmodule then share a common optical axis 934 so that images of the user'seye 9310 are captured from directly in front of the eye. In thisarrangement, the polarization state of the image light 9360 is oppositeto that of the light captured by the eye camera because the image light9360 is reflected by the fold mirror 10352 and the light captured by theeye camera is transmitted by the fold mirror 10352.

FIG. 104 shows an illustration of the optics module of FIG. 95 with theadditional element of a controllable light blocking element to improvecontrast in portions of the displayed image and also to improve theappearance of opacity in displayed objects such as augmented realityobjects. Where the controllable light blocking element can operate byabsorbing the incident light or scattering the incident light asprovided, for example, by an electrochromic element, a polymerstabilized liquid crystal or a ferroelectric liquid crystal. Examples ofsuitable light blocking elements includes: 3G Switchable Film fromScienstry (Richardson, Tex.); Switchable Mirror or Switchable Glass fromKent Optronics (Hopewell Junction, N.Y.). The controllable lightblocking element 10420 is shown in FIG. 104 as being attached to thelower surface of the combiner 9320 so that it doesn't interfere with thedisplayed image while blocking see-thru light from the environment 9362.Provided the combiner 9320 is flat, the addition of controllable lightblocking elements 10420 adjacent to the combiner 9320 is easily doneeither by attaching directly to the combiner or attaching to thesidewalls of the optics module housing. The controllable light blockingelement 10420 can have a single area that can be used to block aselectable portion of the see-through light from the environment overthe entire combiner 9320 area thereby enabling a selectable opticaldensity. Alternatively the controllable light blocking element 10420 canprovide an array of areas 10520, as shown in FIG. 105, that can beseparately selectably controlled to block portions of the combiner 9320area that correspond to areas in the displayed image where high contrastareas of the image are located. FIG. 105 shows an illustration of anarray of separately controllable light blocking elements 10520. FIGS.106a, 106b and 106c are illustrations of how the array of separatelycontrollable light blocking elements 10520 can be used. FIG. 106a showshow the array of separately controllable light blocking elements 10520can be put into blocking modes in areas 10622 and non-blocking modes inareas 10623. Where the blocking mode areas 10622 correspond to areaswhere information or objects are to be displayed such as is shown in thecorresponding areas in the illustration of FIG. 106b . FIG. 106c showswhat the user sees when the image of FIG. 106b is displayed with thearray of controllable light blocking elements 10520 used in lightblocking modes 10622 and non-blocking modes 10623. The user then seesthe displayed information or objects overlaid onto a see-through view ofthe environment, but in the areas where information of objects aredisplayed, the see-through view is blocked to improve the contrast ofthe displayed information or object and provide a sense of solidness tothe displayed information or objects.

In addition, FIG. 104 shows a rear optical element 10490 that can be aprotective plate or a corrective optic. The protective plate can beconnected to sidewalls and other structural elements to stiffen thepositioning of the combiner 9320 and to prevent dust and dirt fromgetting onto the inner surface of the combiner 9320. The correctiveoptics can include a prescriptive optic, which includes the ophthalmicprescription (optical power and astigmatism for example) of the user toimprove the viewing experience.

Head mounted displays provide the user with freedom to move their headwhile watching displayed information. See-through head mounted displaysalso provide the user with a see-through view of the environmentwhereupon the displayed information is overlaid. While head mounteddisplays can include various types of image sources, image sources thatprovide sequential color display typically provide higher perceivedresolution relative to the number of pixels in the displayed imagesbecause each pixel provides image content for each of the colors and theimage perceived by the user as a displayed full color image frame isactually the sum of a series of rapidly displayed sequential colorsubframes. For example, the image source can sequentially providesubframe images comprised of a red image, a green image and then a blueimage that are all derived from a single full color frame image. In thiscase, full color images are displayed at an image frame rate thatincludes a series of at least three sequentially colored subframes thatare displayed at a subframe rate which is at least 3× the image framerate. Sequential color images sources include reflective image sourcessuch as LCOS and DLP.

The color breakup that occurs with a sequential color display occursbecause the different color subframe images that together provide theuser with a full color frame image are displayed at different times. Theinventors realized that with sequential color display in a head mounteddisplay, when there is movement of the head-mounted display or movementof the user's eyes, such that the user's eyes do not move in synch withthe displayed image that under such movement conditions the perceivedlocations of each of the sequential color image subframes are differentwithin the user's field of view. This can happen when the user moves hishead and the user's eyes do not follow the same trajectory as the headmounted display, which can be due to the user's eyes moving in a jerkytrajectory as the eyes pause to look at an object in the see-throughview of the environment. Another way this can happen is if an objectpasses through the see-through view of the environment and the user'seyes follow the movement of the object. Due to this difference inperceived locations within the user's field of view, the user sees thesequential color images slightly separated at the edges of objects. Thisseparation of colors at the edge of objects is referred to as colorbreakup. Color breakup may be easily perceived during certain movementsbecause the sequential colors are vividly colored in areas where they donot overlap one another. The faster the user moves their head or thefaster the user's eyes move across the display field of view, the morenoticeable the color breakup becomes, because the different colorsubframe images are separated by a greater distance within the field ofview. Color breakup is particularly noticeable with see-through headmounted displays, because the user can see the environment and theuser's eyes tend to linger on objects seen in the environment as theuser turns his head. So even though the user may turn his head at asteady rotational rate, the user's eye movement tends to be jerky andthis creates the conditions where color breakup is observed. As suchthere are two different conditions that tend to be associated with colorbreakup: rapid head movement and rapid eye movement.

It is important to note that when the user is not moving his head andthe head mounted display is not moving on the user's head, color breakupwill not be observed because the subframe images are provided at thesame positions within the field of view of the user's eyes. Also, if theuser were to move his head and the user moves his eyes in synch with thehead movement, color breakup will not be observed. So movement of thehead mounted display is indicative of conditions that can lead to colorbreakup and is also indicative of the degree of color breakup that canoccur if the user moves his eyes relative to the movement of the headmounted display. Color breakup is less of an issue with head mounteddisplays that do not have see-through to the environment, because onlythe displayed image content is visible to the user and it moves in synchwith the movement of the head mounted display. Color breakup is also notan issue if a monochrome image is displayed with a monochrome lightsource (i.e. there are no sequential color subframes, instead there areonly single color frames) since all the displayed images are comprisedof the same color. Thus, color breakup is an issue that is mostnoticeable with head mounted displays that provide a see-through view ofthe environment.

Systems and methods according to the principles of the present inventionreduce color breakup and thereby improve the viewing experience providedby a head-mounted display with see-through when the user is movingthrough the environment.

In embodiments, systems and methods are provided where the head-mounteddisplay detects the speed of movement of the head-mounted display and inresponse, the resolution of the image is reduced or the bit depth of theimage is reduced, while the image frame rate at which the image isdisplayed and the associated subframe rate are correspondinglyincreased. In this way, the bandwidth associated with the display of theimage can be maintained constant, in spite of the frame rate beingincreased. Where, by increasing the frame rate associated with thedisplay of images, the time between the display of each sequential colorsubframe image is reduced and as a result the visually perceivedseparation between the sequential color images is reduced. Similarly theimage frame rate can be reduced while the subframe rate is increased byincreasing the number of subframes displayed for each image frame.

In further embodiments, systems and methods are provided where thesequential color subframe images are shifted laterally or verticallyrelative to one another by a number of pixels that corresponds to thedetected movement of the head mounted display. In this way, the colorsequential subframe images are displayed to the user such that they arevisually overlaid on top of each other within the displayed field ofview. This compensates for separation between subframes and therebyreduces color breakup.

In yet another embodiment, systems and methods are provided where aneye-imaging camera in the head-mounted display is used to track themovement of the user's eyes. The movement of the head-mounted displaymay be simultaneously measured. An accommodation in the presentation maythen be made to reduce color breakup. For example, the resolution of theimages and the frame rate may be changed or the image frame rate can bereduced while increasing the subframe rate, in correspondence to thedifference in movement of the user's eyes and the movement of the headmounted display. As another example, the subframes may be shifted toalign the subframes in correspondence to the determined difference inmovement between the user' eyes and the head mounted display. As afurther example, the color saturation of the content may be reduced toreduce the perception of color breakup due to the fact that the colors,while positionally separated as perceived by the user, are not asseparated in color space. In yet a further example, the content could beconverted to monochrome imagery which is displayed as a single colorimage (e.g. white) during the detected movement so that color breakup isnot visible.

FIG. 107 shows an example of a full color image 10700 that includes anarray of pixels, including portions of red, green and blue pixels. Forsequential color display, three subframe images are created that areeach comprised of only one color, such as only red or only green or onlyblue. Those skilled in the art will recognize that sequential colorimages that together provide a perceived full color image can also becomprised of subframes of cyan, magenta and yellow. These subframeimages are rapidly displayed in sequence to the user on the head-mounteddisplay so that the user perceives a full color image that combines allthree colors. With a reflective display such as an LCOS or a DLP, thesubframe images are displayed by changing the reflective display toprovide the respective image content associated with the particularsubframe image and then illuminating the reflective display with theassociated color light, so the light is reflected to provide thesubframe image to the optics of the head-mounted display and from thereto the user's eye.

If the subframe images are accurately aligned with each other, then thefull color image perceived by the user will be full color out to theedges of the image and there will be no color breakup. This is what istypically seen by the user of a head-mounted display when thehead-mounted display is stationary on the user's head and the user isnot moving his eyes. However, if the user moves his head or thehead-mounted display moves on the user's head (such as due to vibration)and the user's eyes are not moved in unison with the displayed image,the user will perceive the subframe images to be laterally (orvertically) offset relative to one another as shown by illustrations10802 and 10804 in FIGS. 108A and 108B. The perceived amount of lateraloffset between the displayed subframe images is related to the speed ofmovement of the head-mounted display and the time between the display ofthe sequential subframe images, which is also known as subframe time or1/subframe rate. The lateral shifting between subframe images, that isperceived by the user, is the color breakup and color breakup isperceived as fringes of color at the edges of objects. When the usermoves his head (or eyes) quickly and the subframe rate is slow, colorbreakup can be substantial as illustrated in FIG. 108A. If the usermoves his head slowly or the subframe rate is higher, the color breakupis less as illustrated in FIG. 108B. If the color breakup is less thanone pixel, in digital imaging, in lateral shifting, the user willperceive there to be no color breakup.

Display frame rate in a head-mounted display is typically limited byeither the bandwidth of the processor and associated electronics or bythe power required to drive the processor and associated electronics,which translates into battery life. The bandwidth required to displayimages at a given frame rate is related to the number of framesdisplayed in a period of time and the number of pixels in each frameimage. As such, simply increasing the frame rate to reduce color breakupis not always a good solution as it requires a higher bandwidth whichthe processor or associated electronics may not be able to support andpower usage will be increased thereby reducing battery life. Instead,systems and methods in accordance with the principles of the presentinvention provide a method of display wherein the number of pixels ineach subframe image is reduced thereby reducing the bandwidth requiredto display each subframe image while simultaneously increasing thesubframe rate by a corresponding amount to maintain bandwidth whilereducing color breakup. This embodiment is suitable for situationswherein subframe images can be provided with different numbers of pixelsand different frame rates. For example, it would be suitable in cameraand display systems where the capture conditions can be changed toprovide images with a lower resolution that can then be displayed with afaster subframe rate. Static images such as text or illustrations can bedisplayed with a lower frame rate and a faster subframe rate to reducecolor breakup since the image content doesn't change quickly.Alternatively, images can be modified to be displayed at lowerresolution (fewer pixels) with a faster frame rate or subframe rate toreduce color breakup

FIG. 109 shows an illustration of the timing of a sequential color imagecomprised of sequential display of a red subframe image 10902 followedby a green subframe image 10904 followed by a blue subframe image 10908in a repeating process. As long as the subframes together are displayedat a full color image frame rate that is greater than approximately 24frames/sec, such that the sequential color subframes are displayed at asubframe rate of greater than 72 subframes/sec, the human eye willperceive full color moving images without flicker. This condition issuitable for displaying a video image without color breakup when thehead-mounted display is stationary or moving relatively slowly. However,if the user moves his head such that the head-mounted display movesrapidly, color breakup will occur. This color breakup occurs becauserapid head movements are typically a reaction of the user to somethingoccurring in the environment (e.g. a loud noise) so that the user's eyesare searching the environment during the rapid head movement, whichleads to jerky eye movements and substantial color breakup.

Movement of the head-mounted display can be detected by an inertialmeasurement unit, which can include accelerometers, gyro sensors,magnetometers, tilt sensors, vibration sensors, etc. Where only themovements within the plane of the display field of view (e.g. x and ymovements and not z movement) are important for detecting conditionswhere color breakup may occur. If the head-mounted display is detectedto be moving above a predetermined threshold where color breakup ispredicted to occur (e.g. greater than 9 degrees/sec), in embodiments,the resolution of the images may be reduced (thereby reducing the numberof pixels in the images and effectively making each pixel larger withinthe display field of view) and the subframe rate may be correspondinglyincreased. Note that the subframe rate can be increased without changingthe image frame rate by increasing the number of subframes that aredisplayed sequentially, for example six subframes could be displayed foreach image frame wherein the sequential color subframe images are eachdisplayed twice. By increasing the number of subframes displayed foreach image frame, the subframe rate can be increased without having toincrease the image frame rate, which can be more difficult to changebecause the image frame rate is typically provided by the source of theimage content such as in a movie. FIG. 110 shows an illustration of afaster subframe rate, wherein the display time for each subframe, 11002,11004, and 11008 is reduced and the time between display of eachsequential subframe is also reduced. FIG. 110 shows a subframe rate thatis approximately twice as fast as that shown in FIG. 109. The associatedimage frame rate can be twice as fast in FIG. 110 as compared to FIG.109, where both the image frame rate and the subframe rate are doubled.Alternatively, as previously described, the image frame rate can beunchanged between FIGS. 109 and 110, where only the subframe rate isdoubled to reduce color breakup. To enable the bandwidth associated withthe display of the images shown in FIG. 110 to be approximately the sameas the bandwidth associated with the display of subframe images shown inFIG. 109, the resolution (number of pixels in each subframe image) isreduced by approximately a factor of two.

While reducing the resolution of the displayed subframe images incorrespondence to an increase in the subframe rate may seem to degradethe image quality perceived by the user, the human eye is not capable ofperceiving high resolution when there is substantial movement. As such,color breakup is more visible than a reduction in the resolution of theimage when the eye is moving. Consequently, the systems and methods ofthe present invention trade reduced image resolution for increased imageframe rate to reduce color breakup without a perceptible loss inresolution, and bandwidth is thereby maintained. This technique can beused, for example, to reduce color breakup by a factor of up to 16,where the resolution of the displayed image is reduced to 1/16th theoriginal resolution and the frame rate of the displayed image isincreased by 16×.

In another embodiment of the invention, when movement of thehead-mounted display is detected, the subframe images associated with afull color frame image are digitally shifted relative to one another ina direction counter to the detected direction of movement and with anamount that corresponds to the detected speed of movement. Thiseffectively compensates for the perceived offset between the displayedsubframe images that causes color breakup. The digital shifting isapplied only to the subframes that together comprise a full color frameimage. This is different from typical digital image stabilizationwherein full color frame images are digitally shifted relative to oneanother to compensate for movement as described, for example, in UnitedStates patent publication 2008/0165280. By applying the digital shiftingto the subframes that constitute a single full color frame image, theamount of digital shifting required to reduce color breakup is typicallyonly a few pixels even when the detected movement speed is high, this isin contrast to typical digital image stabilization where fast movementsresult in accumulating shifts of the frame image so that the imageeffectively moves outside of the display field of view or the amount ofdigital stabilization that can be applied is limited. FIGS. 111a and111b illustrate this embodiment. FIG. 111a shows how sequentiallydisplayed subframe images, 11102, 11104, and 11108 would be perceived bythe user when there is substantial movement, wherein the differentcolors associated with the subframes are separately visible along theedges of objects, evenly spaced across the field of view in thedirection of movement. In contrast, FIG. 111b shows how the visibilityof the subframes is changed when the subframes are digitally shifted tocompensate for the detected movement and thereby reduce the separationbetween the subframes across the field of view, and as a result the userperceives a series of full color frame images 11120 with reduced colorbreakup. As shown in FIG. 111b , the full color frame images are notimage stabilized or digitally shifted in response to the detectedmovement.

In embodiments, movement direction and speed of the head-mounted displayis detected by the IMU sensor immediately prior to the display of eachfull color frame image. If the movement speed is above a predeterminedthreshold, the sequentially displayed color subframes associated witheach full color frame are digitally shifted relative to one another sothat they are displayed in an aligned position within the display fieldof view. The magnitude of the shift corresponds to the speed of thedetected movement and the direction of the shift is counter to thedetected direction of movement.

In an example, the movement of the head-mounted display is detectedimmediately prior to display of a first subframe associated with a fullcolor frame image. The first subframe associated with the full colorframe image can then be displayed without a shift. The second subframecan be shifted by an amount and direction that compensates for themovement that occurs between the display of the first and secondsubframes and then is displayed. The third subframe can be shifted by anamount and direction that compensates for the movement that occursbetween the display of the first subframe and the third subframe and isthen displayed. The movement of the head-mounted display is thendetected again to determine the shifts to be applied to the subframesassociated with the next full color frame image. Alternatively, thesubframes can be shifted by an amount that compensates for a portion ofthe movement that occurs between the subframes.

In a further example, the direction and speed of movement of thehead-mounted display is detected immediately prior to the display of areference subframe. Subsequent subframes are then shifted to compensatefor movement that occurs between the time the reference subframe isdisplayed and the time that the subsequent subframe is displayed.Wherein the time that the reference subframe is displayed and the timethat the subsequent subframe is displayed may be up to 5 frame times.

An advantage of this embodiment is illustrated by examining theeffective frame rates associated with the color breakup and the blur ofthe image. If the full color image is displayed with an image frame rateof 60 frames/sec, the subframes would typically be displayed at asubframe rate of 180 frames/sec to provide three subframes for eachimage frame. The described system and method effectively shifts thesubframes so that they are positioned on top of one another, so thecolor breakup is reduced to an amount that corresponds to 180frames/sec. At the same time, the blur perceived by the user betweenimage frames corresponds to 60 frames/sec since each of the subframes isderived from the same full color frame image.

In further embodiments, the digital shifting of the subframes that isbased on detected movement immediately prior to the display of each fullcolor frame image can be combined with digital image stabilization thatis applied between the full color frame images.

In yet further embodiments, the method of digital shifting of subframesis combined with the method of increasing frame rate with a simultaneousreduction in image resolution. These two methods of reducing colorbreakup operate on different aspects of the image processing associatedwith displaying an image in a head mounted display, as such they can beindependently applied in either order in the image processing systemassociated with the processor.

In yet another embodiment, the head mounted display includes a camerafor detecting the eye movements of the user (e.g. as described herein)relative to the movement of the head mounted display. The eye camera canbe used to measure the speed of eye movement and the direction of eyemovement. In embodiments, the resolution of eye cameras can berelatively low (e.g. QVGA or VGA) so that the frame rate can berelatively high (e.g. 120 frames/sec) without introducing bandwidthlimitations. The detected eye movements relative to the head-mounteddisplay can be used to determine when to apply methods to reduce colorbreakup including, for example, increasing the frame rate and digitallyshifting the subframes as has been previously described herein. Forexample, if the detected eye movement is above a predetermined angularspeed, the resolution of the displayed images can be reduced and thesubframe rate can be increased. In another example, the detected eyemovement can be used to determine the amount and direction of digitalshifting applied to subframes within an image frame prior to display ofthe subframes. In yet another example, measured eye movements can beused in combination with detected movements of the head-mounted displayto determine the amount and direction of digital shifting applied tosubframes within an image frame prior to display of the subframes. Theamount and direction of digital shifting applied to the subframes can bein correspondence to the difference between the detected movements ofthe head mounted display and the detected eye movements of the user.Where the detection of a condition where the user's eye is moving onedirection and the head mounted display is moving in an opposingdirection represents a situation where particularly bad color breakupcan occur. In this case, combined methods for reducing color breakup areadvantageous.

In another yet further embodiment, when movement of the head-mounteddisplay or eye movement is detected above a predetermined threshold, theimages are changed from color sequentially displayed full color imagesto monochrome images. The monochrome images can be comprised of combinedimage content from each of the color sequential subframes associatedwith each full color image frame. Where the monochrome images can begrey scale or luma images wherein the luma code values (Y) for eachpixel can be calculated for example as given in Equation 1 below astaken from http://en.wikipedia.org/wiki/Grayscale and as referenced tothe CIE 1931 standard for digital photograpby:

Y=0.2126R+0.7152G+0.0722B  Equation 1

Where R is the red code value for the pixel, G is the green code valuefor the pixel and B is the blue code value for the pixel. Alternatively,monochrome images can be comprised of single color images such as thegreen subframe image, and this image can be displayed either with asingle color or preferably with simultaneous application of all thesequential colors (e.g. red, green and blue) so that the appliedillumination onto the reflective image source is white light and as aresult, the displayed image appears as a grey scale image.

Several more specific examples are provided below.

Example 1

For a 26 deg display field of view and a 1280 pixel horizontally wideimage, a pixel occupies 0.020 deg within the display field of view. Ifthe frame rate of the full color images is 60 Hz, with three colorsequential subframes images, the subframe time is 0.006 sec. Therotational speed of the head mounted display needed to produce one pixelof color breakup is then 3.6 deg/sec. If the number of horizontal pixelsin the display field of view is reduced to 640 pixels and simultaneouslythe frame rate of the full color images is increased to 120 Hz, withthree color sequential subframes images, the subframe time is reduced to0.003, the size of a pixel is increased to 0.041 deg and the rotationalspeed to produce one pixel of color breakup is 14.6 deg/sec.

Example 2

For a 26 deg display field of view and a 1280 pixel horizontally wideimage, a pixel is 0.020 deg within the display field of view. If thesmallest size that the user can detect for color breakup is one pixelwide, then a rotational speed of over 3.6 deg/sec is required if thesubframe rate is 180 Hz, before color breakup is detected by the user.Even though the color breakup is an analog effect, the user's eye doesnot have the resolution to detect the color fringes that are presentduring movement below this speed. So below this rotational speed, colorbreakup management is not required.

Example 3

For a 26 deg display field of view and a 1280 pixel horizontally wideimage, a pixel is 0.020 deg within the display field of view. If theuser can detect color breakup as small as one pixel wide, then arotational speed of 3.6 deg/sec will require a shift of the subframesrelative to each other of one pixel if the subframe rate is 180 Hz, toalign the subframes so that color breakup is not visible to the user. Ifthe user rotates their head at 15 deg/sec, then the subframes willrequire a shift of 4 pixels relative to one another to align thesubframes so that color breakup is not visible. If the image framebegins with the display of the red subframe image, then no digitalshifting is required for the red subframe image. A 4 pixel shift isrequired for the green subframe image. And, an 8 pixel shift is requiredfor the blue subframe image. The next red subframe associated with thenext image frame would then be effectively shifted 12 pixels relative tothe previous red subframe within the field of view.

Each of the color breakup reduction technologies described herein may beused in combination with each of the other color breakup reductiontechnologies.

The inventors appreciated that fitting see-through computer displaysinto certain head-worn form factors is a challenge, even when reduced insize as described herein. A further advantage that is provided by anoptics module that includes multiply folded optics is that twists can beintroduced at the fold surfaces to modify the orientation of differentportions of the optics module relative to each other. This can beimportant when the optics module needs to fit into a thin curved glassesframe, a visor or a helmet where the increased width associated with theupper portion of the multiply folded optics module can make it moredifficult to fit into structures that are not parallel to the combiner.As such, another aspect of the present invention relates to twistingcertain optical components within the see-through computer display suchthat the optical components better fit certain form factors (e.g.glasses) yet continue to perform as high quality image displays. Inembodiments, optics systems with dual mirror systems to fold the opticalpath (e.g. optical systems described herein with respect to FIG. 6, and93 through 106) are provided such that the image production module (e.g.upper module), which includes a first image light reflective surface, isturned about a first optical axis leading from the upper module to thelower module and in a direction to fit the upper module more compactlyinto a frame of a head-worn computer. At the same time, to avoiddistorting the image provided to the eye of the user, the image deliveryoptics (e.g. lower module), which includes a second image lightreflective surface, is turned about a second optical axis that leads tothe user's eye and in the opposite direction relative to the image,thereby introducing a compound angle between the first image lightreflective surface and the second image light reflective surface.Provided that the first and second optical axes are perpendicular to oneanother in the non-twisted state, the distortion in the image associatedwith the twist about the first axis is compensated by a twist of thesame angular magnitude about the second axis so that the image presentedto the eye of the user is undistorted by the twisting.

FIG. 112 illustrates a head-worn computer with see-through displays inaccordance with the principles of the present invention. The head-worncomputer has a frame 11202 that houses/holds the optics modules inposition in front of the users eyes. As illustrated in FIG. 112, theframe 11202 holds two sets of optical modules 11204 and 11208 each ofwhich have upper and lower optics modules. Optics module 11204 isnon-twisted and is presented to illustrate the difficulty in fitting thenon-twisted version into the frame. One will note that the dotted box,which represents the outer bounds of the optics module 11204 doesn't fitwithin the bounds of the frame 11202. Fitting optics module 11204 intothe frame 11202 would normally require that the frame 11202 becomethicker, from front to back, which would lead to more offset of theglasses form factor from the face of the user, which is less desirableand is less compact. In contrast, optics module 11208 is a twistedoptics module, where the upper module is twisted (or rotated) to betterfit into the confines of the frame 11202 as shown in FIG. 112. FIG. 113shows a more detailed illustration of the twists imparted withinmultiply folded optics in optics module 11208. Upper module 11214 istwisted relative to the lower module 11218 along optical axis 934 tobetter fit into the frame 11202, it is this twist which enables opticsmodule 11208 to better fit within the frame 11202 as shown in FIG. 112and as a result frame 11202 can be thinner and more compact than ifnon-twisted optics modules were used. To avoid distorting the imageprovided to the user, a second twist is required to introduce a compoundangle between the first reflecting surface 11225 in the upper module11214 and second reflecting surface 11226 in the lower optics module11218. The second twist is imparted to the second reflecting surfaceabout the optical axis 933 and in an opposite direction relative to theimage from the twist in the upper module 11214. In this way, the effectsof the increased width of the upper portion of the multiply foldedoptics can be reduced when fitting the optics module into a curvedstructure such as glasses frames, a visor frame or a helmet structure.Where it is preferred, but not required that the optical axis 934 beperpendicular to the optical axis 933 so that the magnitude of theangular twist imparted to the first reflecting surface 11225 can be thesame as the twist imparted to the second reflecting surface 11226 toprovide an image to the user's eye that is not distorted due to thetwisting.

Another aspect of the present invention relates to the configuration ofthe optics and electronics in a head-worn frame such that the framemaintains a minimal form factor to resemble standard glasses. Inembodiments, a see through optical display with multiply folded opticsto provide a reduced thickness (e.g. as described herein) may be mountedin the frame. In embodiments, the multiply folded optical configurationmay be twisted at the fold surfaces (e.g. as described herein) to betterfit the optics into the frame. In embodiments, the electronics thatoperate the displays, processor, memory, sensors, etc. are positionedbetween, above, below, on a side, etc. of the optical modules andoriented to provide a reduced thickness in the frame to match thethickness of the optics. Orienting the board can be particularlyimportant when the board includes large components that limit the widthof the board, such as for example the processor chip. For example, anelectronics board or components on the electronics board may be mountedin a vertical orientation between and/or above the optical modules toreduce the thickness of the electronics board as mounted into the frame.In another configuration the board may be mounted between the opticalmodules at a height near the top of the optical modules to minimize theheight of the glasses frame. In yet another configuration the board maybe mounted such that it extends over the optical modules to minimize thethickness of the frame. In further embodiments, the board may be mountedin an angled configuration to enable the thickness and height of theframe to be reduced simultaneously. In embodiments, the electronics maybe divided between multiple boards. For example, a longer board over ashorter board where the space between the optical modules is used forthe lower board. This configuration uses some of the space between theeyes for some of the electronics.

FIG. 114 illustrates a top view and front view of a configurationincluding optical modules 11208, electronics board 11402 and a heat sink11404. The board 11402 is mounted in a vertical orientation to maintaina thin frame portion that sits across the user's brow. As illustrated,the optical modules 11208 include upper modules 11214 and a secondreflecting surface 11226 in front of the user's eye. The upper modulemay have a flat reflecting surface and the upper 11214 may be turned ortwisted with respect to the second reflecting surface 11226 as describedherein. The second reflecting surface 11226 may be a partial mirror,notch filter, holographic filter, etc. to reflect at least a portion ofthe image light to the eye of the user while allowing scene light totransmit through to the eye.

FIG. 115 illustrates a front view of a configuration that includesoptics illustrated in FIG. 114; however, the electronics board 11402 ismounted in the space between the optical modules at a height that issimilar to the height of the optical modules. This configuration reducesthe overall height of the frame.

FIG. 116 illustrates a front view of a configuration that includesoptics illustrated in FIGS. 114 and 115. The electronics layout in thisconfiguration is done with multiple boards, 11402, 11602 and 11604. Themultiple board configuration allows the boards to be thinner from frontto back thereby enabling the brow section of the frame to be thinner. Aheat sink 11404 (not shown in FIG. 116) may be mounted on the front facebetween the optical modules. This configuration also causes the heat tobe drawn in a direction away from the user's head. In embodiments, theprocessor, which is a main heat generator in the electronics, is mountedvertically (e.g. on board 11604) and the heat sink 11404 may be mountedin front such that it contacts the processor. In this configuration, theheat sink 11404 causes heat to spread to the front of the device, awayfrom the user's head. In other embodiments, the processor is mountedhorizontally (e.g. on board 11602 or 11402]. In embodiments, theboard(s) may be tilted (e.g. 20 degrees) from front to back to create aneven thinner brow section.

Another aspect of the present invention relates to concealing theoptical modules such that a person viewing the user does not clearly seethe optical modules, electronics or boards. For example, inconfigurations described herein, the optical modules include lenses thathang below the top of the brow section of the head-worn device frame andthe electronics board(s) hang down as well so that the see-through viewis partially blocked. To conceal these features and thereby provide thehead worn computer with the appearance of conventional glasses, an outerlens may be included in the glasses frame so that it covers a portion ofthe frame that contain the optical modules or electronics, and the outerlens may include a progressive tint from top to bottom. In embodiments,the tint may have less transmission at the top for concealment of aportion of the frame that includes the optical modules or electronicsboard while having higher transmission below the concealment point suchthat a high see-through transmission is maintained.

Aspects of the present invention provide multiply folded optics toreduce the thickness of the optics modules along with verticallyoriented or angled electronics to reduce the mounted thickness of theelectronics and progressively tinted outer lenses to conceal a portionof the optics or electronics. In this way, a head worn computer isprovided with a thinner form factor and an appearance of conventionalglasses.

Another aspect of the present invention relates to an intuitive userinterface mounted on the HWC 102 where the user interface includestactile feedback to the user to provide the user an indication ofengagement and change. In embodiments, the user interface is a rotatingelement on a temple section of a glasses form factor of the HWC 102. Therotating element may include segments such that it positively engages atcertain predetermined angles. This facilitates a tactile feedback to theuser. As the user turns the rotating element it ‘clicks’ through itspredetermined steps or angles and each step causes a displayed userinterface content to be changed. For example, the user may cycle througha set of menu items or selectable applications. In embodiments, therotating element also includes a selection element, such as apressure-induced section where the user can push to make a selection.

FIG. 117 illustrates a human head wearing a head-worn computer in aglasses form factor. The glasses have a temple section 11702 and arotating user interface element 11704. The user can rotate the rotatingelement 11704 to cycle through options presented as content in thesee-through display of the glasses. FIG. 118 illustrates severalexamples of different rotating user interface elements 11704 a, 11704 band 11704 c. Rotating element 11704 a is mounted at the front end of thetemple and has significant side and top exposure for user interaction.Rotating element 11704 b is mounted further back and also hassignificant exposure (e.g. 270 degrees of touch). Rotating element 11704c has less exposure and is exposed for interaction on the top of thetemple. Other embodiments may have a side or bottom exposure.

As discussed above, a specially designed lens may be used to concealportions of the optics modules and/or electronics modules. FIG. 119illustrates an embodiment of one such lens 11902. Two lenses, 11902 areillustrated with Base 6 and 1.3 mm thickness but other geometries with,for example, different curvatures and thicknesses can be used. Thelenses 11902 are shaped to look like conventional glasses lenses withfeatures including magnetic mounting attachment and special tinting inportions of the lenses 11902 where opaque structures such as electronicsare located behind the lenses.

The lenses 11902 includes blind holes 11904 for the mounting of amagnetic attachment system (not shown). The magnetic attachment systemmay include magnets, magnetic material, dual magnets, oppositepolarization magnets, etc. such that the lenses 11902 can be removed andremounted to the head-worn computer (e.g. HWC 102). In the magneticattachment system, the lenses 11902 are held by magnetic force into theframe of the HWC. The magnets can be inserted into the blind holes 11904or inserted into the frame of the HWC in corresponding matchingpositions. As long as either the lens 11902 or the matching position onthe frame of the HWC includes a magnet and the other position has asimilar sized piece of magnetic material or another magnet oriented toattract the lens 11902 and hold it in the frame of the HWC. To this end,the frame of the HWC can provide guidance features to position the lens11902 in front of the optics modules in the HWC. Where the guidancefeatures can be a ridge or flange that the lens is seated in so the lens11902 cannot move laterally when held in place by the magneticattachment system. In this way, the function of the magnetic attachmentsystem is simply to hold the lenses 11902 in place, while the guidancefeatures position the lenses 11902. The guidance features can berobustly made to hold the lenses 11902 in place when dropped orsubjected to impact even when the force provided by the magneticattachment system is relatively low, so that the lenses 11902 can beeasily removed by the user for cleaning or replacement. Where easyreplacement enables a variety of lenses with different optical features(e.g. polarized, photochromic, different optical density) or differentappearance (e.g. colors, level of tinting, mirror coating) to be changedout by the user as desired.

FIG. 119 also illustrates an example of how the lens 11902 may be tintedto conceal or at least partially conceal certain optical components(e.g. the non-see-through components or opaque components) such as,electronics, electronics boards, auxiliary sensors such as an infraredcamera and/or other components. As illustrated, the blind holes 11904may also be concealed or at least partially concealed by the tinting. Asillustrated in FIG. 119, a top portion 11908, approximately 15 mm asillustrated, may be more heavily tinted (e.g. 0 to 30% transmission) ormirrored to better conceal the non-see through portions of the opticsand other components. Below the top portion 1190B, the lens 11902 mayhave a gradient zone 11909 where the tinting level gradually changesfrom top to bottom and leads into the lower zone 11910. The lower zone11910 includes the area where the user primarily views the see-throughsurrounding and this zone may be tinted to suit the viewing application.For example, if the application requires a high see through, the lowerzone 11910 may be tinted, between 90% and 100% transmissive. If theapplication requires some see-through tint, than the lower area may bemore heavily tinted or mirrored (e.g. 20% to 90%). In embodiments, thelower area 11910 may be a photochromic layer, an electrochromic layer, acontrollable mirror or other variable transmission layer. Inembodiments, the entire lens or portions thereof may have a variabletransmission layer such as a photochromic layer, electrochromic layer,controllable mirror, etc. In embodiments, any of the areas or whole lens11902 may include polarization.

Another aspect of the present invention relates to cooling the internalcomponent through the use of micro-holes sized such they are largeenough to allow gas to escape but small enough to not allow water topass through (e.g. 25 μm, 0.2 mm, 0.3 mm, etc.). The micro-holes may beincluded in a heat sink, for example. The heat sink, or other area, maybe populated with hundreds or thousands of such micro-holes. Themicro-holes may be laser cut or CNC holes, for example, that are smallenough to keep large droplets of water out of the device but allow airto exchange through the heat sink. Besides increasing surface area ofthe heat sink, they also have matching holes on the underside of theframe to enable convective cooling where cool air is pulled in from thebottom as the heat raises from the top, like a chimney and as such, theheat sink with the micro-holes is preferably located on the top or sideof the frame of the HWC. In embodiments, the micro-holes are aligned inthe troughs formed by the fins on the top of the heat sink. This causesthe exiting air to flow through the troughs thereby increasing the heattransfer from the fins. In embodiments, the micro-holes may be angledsuch that the length of the hole in the heat sink material is increasedand the air flow can be directed away from the head of the user. Inaddition, the micro-holes may be of a size to cause turbulence in theair flow as it passes through the micro-holes. Where, turbulencesubstantially increases the heat transfer rate associated with the airflow through the heat sink. In embodiments, the heat management systemof the HWC 102 is passive, including no active cooling systems such asfans or other energized mechanical cooling systems to force air flowthrough the micro-holes. In other embodiments, the heat managementsystem includes energized mechanical cooling, such as a fan or multiplefans or other systems to force air movement through the HWC and themicro-holes.

Another aspect of the present invention relates to finding items in thesurrounding environment based on similarity to items identified.Augmented reality is often rigidly defined in terms of what is includedand how it is used, it would be advantageous to provide a more flexibleinterface so people can use augmented reality to do whatever they wantit to do. An example is to use the HWC camera, image analysis anddisplay to designate items to be found. FIG. 122 shows an illustrationof an image 12210 of a scene containing an object that the user wouldlike the HWC to assist in looking for the object as the user movesthrough the environment. In this example, the user has circled theobject 12220 that is being looked for, where in this case the object isa cat. The HWC then analyses the circled region of the image for shapes,patterns and colors to identify the target to be searched for. The HWCthen uses the camera to capture images of the scene as the user movesabout. The HWC analyses the images and compares the shapes, patterns andcolors in the captured images of the scene and compares them to theshapes, patterns and colors of the target. When there is a match, theHWC alerts the user to a potential find. The alert can be a vibration, asound or a visual cue in an image displayed in the HWC such as apointer, a flash or a circle that corresponds to the location of thepotential find in the scene. This method provides a versatile andflexible augmented reality system wherein an item is described visuallyand a command of “find something like this” is given to the HWC.Examples of ways to identify an object to be searched for include:circle an item in a previously captured image that is stored on the HWC(as shown in FIG. 122); point to an item in a physical image held infront of the camera in the HWC; point to an item in the live imageprovided by the camera in the HWC and viewed in the see-through displayof the HWC, etc. Alternately, text can be input to the HWC with acommand of “find wording like this”, e.g. a street sign or an item in astore and the HWC can then search for the text as the user moves throughthe environment. In another example, the user can indicate a color witha command of “find a color like this”. The camera used to search for theitem can even be a hyperspectral camera in HWC to search for the itemusing infrared or ultraviolet light to thereby augment the visual searchthat the user is conducting. This method can be extended to any patternthat the user can identify for the HWC such as sounds, vibrations,movements, etc. and the HWC can then use any of the sensors included inthe HWC to search for the identified pattern as the target. As such thefinding system provided by the invention is very flexible and can reactto any pattern that can be identified by the sensors in the HWC, all theuser has to do is provide an example of the pattern to look for as atarget. In this way the finding system assists the user and the user cando other things while the HWC looks for the target. The finding systemcan be provided as an operating mode in the HWC where the user selectsthe mode and then inputs the pattern to be used as the search target bythe HWC. Examples of items that can be searched for include: householdobjects, animals, plants, street signs, weather activity (e.g. cloudformations), people, voices, songs, bird calls, specific sounds, spokenwords, temperatures, wind direction shifts as identified by wind soundrelative to the compass heading, vibrations, objects to be purchased,brand names in stores, labels on items in a warehouse, bar codes ornumbers on objects and colors of objects to be matched. In a furtherembodiment, the rate of searching (e.g. how often an analysis isconducted) can be selected by the user or the rate can be automaticallyselected by the HWC in response to the rate of change of the conditionsrelated to the target. In a yet further embodiment, the sensors in theHWC include a rangefinder or a camera capable of generating a depth mapto measure the distance to an object in an image captured by the camera.The HWC can then analyze the image along with the distance to determinethe size of the object. The user can then input the size of the objectto the finding system as a characteristic of the target pattern toenable the HWC to more accurately identify potential finds.

Another aspect of the present invention relates to assisting a person inreading text that is presented in a physical form, such as a book,magazine, on a computer screen or phone screen, etc. In embodiments, thecamera on the HWC can image the page and the processor in the HWC canrecognize the words on the page. Lines, boxes, or other indicators maybe presented in the HWC to indicate which words are being captured andrecognized. The user would then be viewing the page of words through thesee-through display with an indication of which words have beenrecognized. The recognized words can then be translated or convertedfrom text that is then presented to the user in the see-through display.Alternately, the recognized words can be converted from text to speech,which is then presented to the user through the head worn speakers,headphones, visual displays, etc. This gives the user a betterunderstanding of the accuracy associated with the text recognitionrelative to the translated text or converted speech.

In a further aspect of the invention, a magnetic attachment structure isprovided for the combiner to enable the combiner to be removable. In theoptics associated with a HWC 102 such as for example the optics shown inFIG. 6, it is important that the combiner 602 be accurately positionedand rigidly held below the frame of the HWC and the upper optical module202 located inside the frame. At the same time, the combiner 602 canbecome damaged so that it needs to be replaced, or it may need to becleaned periodically so that it is advantageous for the combiner to beremovable. FIG. 123 shows an illustration of a cross section of a singlecombiner 12360 with the magnetic attachment structure as shown from theside to show the angle of the combiner 12360. FIG. 124 shows anillustration of two combiners 12360 with magnetic attachment structuresattaching the combiners 12360 to the frame of the HWC 12350 as shownfrom the front of the HWC. The combiner 12360 has two or more pins 12365that are attached to the combiner 12360 such that the pins have parallelaxes. The pins 12365 are shown as being inserted into holes drilledthrough the combiner 12365 and attached in place with adhesive such asUV cured adhesive. The pins 12365 are made of a magnetic material suchas for example 420 stainless steel. The pins 12365 extend into parallelbores in the frame of the HWC 12350 so that the combiner 12360 isfixedly held in place relative to the frame of the HWC 12350. Theattachment and bend of the pins 12365 establish the angle between thecombiner 12360 and the optics in the frame of the HWC 12350. A magnet12370 is bonded into the frame of the HWC 12350 such that the pin 12365attracted by the magnet 12370 and thereby the pin 12365 and the attachedcombiner 12360 are held in place relative to the frame of the HWC 12350.The magnet 12370 is selected so that the force exerted by the magnet12370 onto the pin 12365 is strong enough to hold the combiner 12360 inplace during normal use, but weak enough that removal of the combiner12350 is possible by the user. By having the pins 12365 and associatedbores parallel, the combiner 12350 can be easily removed for cleaning,or replaced if damaged. To provide a more rigid and repeatableconnection between the combiner 12360 and the frame of the HWC 12350,the pins can fit into an extended tight bore in the frame of the HWC12350. In addition, the pins 12365 can include a flange as shown thatseats onto an associated flat surface of the frame of the frame 12350 ora flat surface of the magnet 12370 to further establish the angle of thecombiner 12360 and the vertical position of the combiner 12360. In apreferred embodiment, the magnet 12370 is a ring magnet and the pin12365 extends trough the center of the ring magnet. The magnet 12370 canalso be included in an insert (not shown) that further includes aprecision bore to precisely align and guide the pin 12365. The insertcan be made of a hardened material such as a ceramic to provide a borefor the pin 12365 that is resistant to wear during repeated removal andreinstallation of the combiner 12360. The pins can be accuratelypositioned within the combiner through the use of a jig that holds thepins and the combiner. The holes for the pins in the combiner are thenmade larger than the pins so there is a clearance to allow the combinerand pins to be fully positioned by the jig. An adhesive such as a UVcuring adhesive is then introduced to the holes and cured in place tofasten the pins to the combiner in a position that is established by thejig. In a further embodiment, the combined structure of the pins 12365and the combiner 12350 are designed to break if subjected to a highimpact force, to thereby protect the user from injury. Where the pin12365 or the combiner are designed to break at a previously selectedimpact force that is less than the impact force required to break theframe of the HWC 12350 so that the combiner 12350 with the attached pins12365 can be simply replaced when damaged. In yet a further embodiment,by providing a method for easily replacing the combiners 12360,different types of combiners can also be provided to the user such as:polarized combiners, combiners with different tints, combiners withdifferent spectral properties, combiners with different levels ofphysical properties, combiners with different shapes or sizes, combinersthat are partial mirrors or combiners that are notch mirrors, combinerswith features to block faceglow as previously described herein.

In typical computer display systems, automatic brightness control is aone dimensional control parameter; when the ambient brightness is high,the display brightness or light source is increased, when the ambientbrightness is low, the display brightness or light source is decreased.The inventors have discovered that this one-dimensional paradigm hassignificant limitations when using see-through computer displays.Aspects of the present invention relate to improving the performance ofthe head-worn computer by causing it to understand the relativebrightness of the content to be presented in addition to understandingthe brightness of the surrounding environment and to then adjust thebrightness of the content, based on both factors, to create a viewingexperience that has the appropriate viewability.

An aspect of the present invention relates to improving the viewabilityof content displayed in a see-through head-worn display. Viewabilityinvolves a number of factors. The inventors have discovered that, inaddition to image resolution, contrast, sharpness, etc., the viewabilityof an image presented in a see-through display is effected by (1) thesurrounding scene that forms the backdrop for the image, and (2) therelative or apparent brightness of the image displayed. If the user, forexample, is looking towards a bright scene, the viewability of thepresented content may be washed out our or hard to see if the displaysettings are not altered and, in the event that the content itself isrelatively low in brightness (e.g. the content has a lot of dark colorsor black areas in it), it may continue to be washed out unless thecontent is also altered. In this situation, the brightness of thedisplay may be increased even higher than what would normally berequired in a dark environment in order to compensate for the darkcontent of the image. As an additional example, if the user is lookingtowards a dark scene, the presented content may be perceived by the useras overly bright and washing out the scene, or making it hard tointeract with the scene if the display settings are not altered. Inaddition, if the content itself is relatively bright (e.g. mainly lightcolors or areas of white content), the content may require furtheralteration to obtain the proper viewability. In this situation, thedisplay brightness may be decreased further than if it were onlydependent on the environmental lighting conditions to make theviewability of the content appropriate. In embodiments, the head-worncomputer is adapted to measure the scene that forms the backdrop for thepresented content, understand the relative brightness of the contentitself (i.e. the innate content brightness) to be presented and thenadjust the presentation of the content based on the scene brightness andthe innate content brightness to achieve a desired content viewability.

While embodiments herein use the terms “content brightness” and “displaybrightness” in the context of altering the viewability of the content,it should be understood that the step of making the alteration incontent and/or display in response to meeting a viewability need mayinclude causing the system to leave the image content alone and increasethe light source brightness of the display, use the available light andincrease the digital brightness of the image content by adjusting theparameters of the entire display using the display driver, adjust theactual content that is being displayed, etc. The viewability adjustmentmay be made by adjusting a lighting system used to illuminate areflective display (e.g. changing the pulse width modulation duty cycleof the LEDs, changing the power delivered to the lighting system, etc.),changing the brightness settings of an emissive display, changing anaspect of how the display presents all content by adjusting settings inthe display driver or changing an aspect of the content its self throughimage processing (e.g. changing brightness, hue, saturation, color value(e.g. red, green, blue, cyan, yellow, magenta, etc.] exposure, contrast,saturation, tint, etc.), of the all the content, select regions of thecontent, types of content which may be shown at the same time but haveinnate differences in visibility regardless of location, etc.

To improve the viewing experience for a user when viewing content in asee-through head-worn display, the visual interaction between thedisplayed image and the see-through view of the environment must beconsidered. The viewability of a given displayed image is highlydependent on a variety of attributes such as its size, color, contrastand brightness as well as the perceived brightness as seen by the user.Where the color and brightness of the displayed image can be determinedby the pixel code values within the digital image (e.g. average pixelcode). Alternatively, the brightness of the displayed image can bedetermined from the luma of the displayed image (see “BrightnessCalculation in Digital Image Processing”, Sergey Bezryadin et. al.,Technologies for Digital Fulfillment 2007, Las Vegas, Nev.). Otherattributes of the displayed image can be calculated based the code valuedistributions in the image similar to the brightness. Depending on themode of operation, the type of activity the user is engaged in and aperceived brightness of the image being displayed, it may be importantfor the displayed image to match the see-through view of theenvironment, contrast with the see-through view of the environment, orblend into the see-through view of the environment. The contentadjustment may be based on the perceived user need in addition to thescene that will form the backdrop for the content. Embodiments providemethods and systems to automatically adjust viewability of the imagedepending on, for example:

1. the percent of the display field of view that is covered by displayedcontent, (where in a see-through head worn display the portions of thedisplayed image that are black are seen as portions with no displayedcontent and instead the user is provided with a see-through view of theenvironment in that portion);

2. a brightness metric of image being displayed (e.g. hue, saturation,color, individual color contribution (e.g. red content, blue content,green content) average brightness, highest brightness, lowestbrightness, statistically calculated brightness (e.g. mean, median,mode, range, distribution concentration), etc.);

3. sensor feed back indicative of a user use scenario (e.g. the amountof motion measured by sensors in the IMU in the head-worn display usedto determine that the user is stationary, walking, running, in a car,etc.);

4. the operating mode of the head-worn display (which can be selected bythe user or automatically selected by the head-worn display based on forexample: the environmental conditions, the GPS location, the time ordate, indicated or determined user scenario).

5. the type of content (e.g. still pictures (e.g. either high or lowcontrast, monochrome or color such as icons or markers), moving pictures(e.g. either high or low contrast, monochrome or color such as scrollingicons on our launcher or a bouncing marker), video content (e.g. wherelocation and intensity of pixels are varying such as a bouncing andblinking marker, other normal types of video content like Hollywoodmovies, step-by-step tutorials or your last run down the ski sloperecorded on your glasses), text (e.g. small, large, monochrome,outlined, blinking, etc.), etc.; and/or

6. a user use scenario (e.g. a predicted scenario based on sensorfeedback, based on an operating application, based on a user setting)such as sitting still in a safe location such as your living room andviewing a movie (e.g. where it might not need to defeat ambient),walking around and getting notifications or viewing turn-by-turndirections (e.g. where it might depend on the amount of display coveredbut probably best to match ambient), driving in a car and erasing theblind spots such as vertical pillars (e.g. where it may need to matchambient), driving in a car and trying to display HUD data over theexternal illumination (e.g. where it may need to defeat ambient),getting instructions on repairing and engine (e.g. where some areas needto defeat ambient such as pages in the service manual and some need tomatch such as augmented overlays where you still need to see what you'reworking on), etc.

For example, in a night vision mode using the camera with a live feed tothe head-worn display, sensors associated with the head-worn displayindicate that the user is moving at a speed and with an up and downmovement that indicates jogging. As a result, the head-worn display canautomatically determine that the displayed images should be providedwith a brightness that provides good viewing without regard to thesee-through view of the surrounding environment since it is too dark forthe user to see a see-through view of the environment. In addition, thehead-worn display may switch the displayed image from full color to amonochrome image such as green where the human eye is more sensitive andthe human eye responds faster.

In another example of a mode, the brightness of the displayed image isincreased relative to the see-through view of the surroundingenvironment when eye tracking is being used in a user interface. In thisembodiment, the type of user interface being used determines thebrightness of the displayed image relative to the brightness of thesee-through view of the surrounding environment. In this way, thesee-through view is made to be dimmer than the displayed image so thatthe see-through view is made less noticeable to the user. By making thesee-through view less noticeable to the user, the user can more easilymove his eyes to control the user interface without being distracted bythe see-through view of the surrounding environment. This approachreduces the jittery eye movement that is typically encountered whenusing eye tracking in a head mounted display that also provides the usera see-through view of the environment. FIG. 126 is a chart that showsthe brightness (L*) perceived by the human eye relative to a measuredbrightness (luminance) of a scene. In this chart, it can be readily seenthat the human eye has a non-linear response to luminance wherein theeye is more sensitive to differences at lower levels and less sensitiveto differences at higher levels. In embodiments, the displayed image canbe provided with an average brightness that is perceived as being 2× ormore brighter than the average brightness of the see-thru view of theenvironment (i.e. L* of the displayed image is 2× the L* of the see-thruview) when using a mode that includes eye tracking control of a userinterface.

Further, the displayed image can be changed in response to the averagecolor, hue or spatial frequency of the environment surrounding the user.In this case, a camera in the head-worn display can be used to capturean image of the environment that includes a portion of the see-throughfield of view as seen by the user. Attributes of the captured image ofthe environment can then be digitally analyzed as previously describedherein to calculate attributes for the displayed image. In this case,the attributes of the captured image of the environment can include anaverage brightness, a color distribution or spatial frequency of thesee-through view of the environment. The calculated attribute of theenvironment can then be compared relative to attributes of the imagebeing displayed to determine how distracting the see-through view willbe versus the type of displayed image being displayed. The attributes ofthe displayed image can then be modified in terms of color, hue orspatial frequency to improve the viewability in the head-worn displaywith see-through. This comparison of image content versus see-throughview and the associated modification of the displayed image can beapplied within large blocks of the field of view or within smalllocalized blocks of the field of view comprised of only a few pixelseach such as may be required for some types of augmented realityobjects. Wherein the captured image of the environment that is used tocalculate the attributes of at least a portion of the see-through viewof the environment provided to the user does not have to be the sameresolution as the displayed image. In a further embodiment, a brightnesssensor or a color sensor included in the head-worn display can be usedto measure the average brightness or average color within a portion ofthe see-through field of view of the environment. By using a dedicatedsensor for measuring brightness or color, the calculation of theattribute in the see-through view of the environment can be providedwith little processing power thereby reducing the power required andincreasing the speed of the calculation.

It has often been said that color is very subjective and there areseveral reasons for this including things like dependencies on ambientlighting of the environment, the proximity of other colors and whetheryou are using one eye or two. To compensate for these effects, thehead-worn display may measure the color balance and intensity of theambient light either with a light sensor or with a camera to infer howcolors of objects in the environment will appear, then the color of thedisplayed image can be modified to improve viewability in the head-worndisplay with see-through. In the case of augmented reality objects,viewability can be improved by rendering the augmented reality object sothat it better contrasts with the environment for example for a marker,or the so that it blends into the environment for example when viewingarchitectural models. To this end, light sensors can be provided todetermine the brightness and color balance of the ambient lighting infront of the user or from other directions in the environment such asabove the user. In addition, objects in the environment can beidentified that typically have standard colors (e.g. stop signs are red)and these colors can be measured in a captured image to determine theambient lighting color balance.

Color perception by the human eye gets even more complicated at theextremes of very bright and very dark, because the human eye respondsnon-linearly. For example in direct sunlight, colors begin to wash outas nerves in the brain begin to saturate and lose the ability to detectsubtle differences in color. On the other hand, when the environment isdim, the contrast perceived by the human eye decreases. As such, whenbright conditions are detected, colors can be enhanced in the displayedimage. When dim conditions are detected, the contrast in the displayedimage can be enhanced to provide a better viewing experience for theuser. Where contrast can be enhanced by digitally sharpening the image,increasing the code value differences between adjacent areas in thedigital image or by adding a narrow line comprised of a complimentarycolor around the edge of displayed objects.

In dim conditions, color sensitivity of the human eye varies by color aswell, so that blue colors look brighter than red colors. As a result, indim viewing conditions, the color of objects changes toward the blue.Consequently, when the displayed image is provided as a dim image suchas for example when using the head-worn display in dim lighting whereviewability of both the displayed image and the see-through view areimportant, the color balance of the image can be shifted to be more redto provide a more accurate color rendition of the displayed image asperceived by the user. If the image is displayed as a very dim image,the image can be further changed to a monochrome red to better preservethe user's night vision.

In embodiments, the head-worn display uses sensors or a camera todetermine the brightness of the surrounding environment. The type ofimage to be displayed is then determined and the brightness of the imageis adjusted in correspondence with the type of image and the operatingmode of the head-worn display. The combined brightness, comprised of thebrightness of the see-through view in combination with the brightness ofthe displayed image, is determined. The operating zone of the human eyeis then determined based on the combined brightness and the knownsensitivity of the human eye as shown in FIG. 125. Attributes of theimage (e.g. color balance, contrast, color of objects, size of text) arethen adjusted to improve viewability in correspondence to the determinedoperating zone, the type of image and the operating mode.

FIG. 125 shows a chart of the sensitivity of the human eye versusbrightness as provided in Chapter 2.1 page 38 in the book by Gonzalez,R. C. and Woods, R. E., “Digital Image Processing Second Edition”,copyright 2002, Prentice Hall Inc ISBN 0-201-18075-8 and also availableat http://users.dccuchile.cl/˜jsaavedr/libros/dip_gw.pdf. As can beseen, the sensitivity is quite non-linear. To make this non-linearityeasier to understand, the chart has been broken up into four zones.

Zone 1: Top end of Photopic vision (glare limit) where relativedifferences in brightness are less noticeable and colors shift to red.Sharpness of focus is good with contracted pupil but glare inside theeye starts to obscure details.

To improve viewability, the displayed image is modified to increasecontrast and increase green and/or blue.

Zone 2: Standard range of color vision where cones dominate in the humaneye. Color perception is basically uniform and brightness perceptionfollows a standard Gamma curve. Maximum sharpness possible due to smallpupil and manageable levels of brightness. Viewability is good withstandard brightness and color.

Zone 3: Transition zone from cones to rods for primary sensitivity.Color perception becomes non-linear as the red cones lose sensitivityfaster than blue and green. Contrast perception is reduced due toflattening response to changes in brightness. Focus sharpness alsobegins to reduce with larger pupils, especially in older eyes thataren't as capable of adapting freely. Viewability is improved byincreasing font and object sizes for legibility and reducing blue andgreen colors while increasing red and increasing contrast.

Zone 4: Bottom end of scotopic vision where rods dominate forsensitivity and motion is more apparent than content. Viewability isimproved by changing the displayed images to eliminate high spatialfrequency such as small text and instead provide iconography and usemotion or blinking to increase visibility of critical items.

In a further embodiment, changes in operating mode are considered. Sothat if the user changes operating mode, the displayed image is modifiedin correspondence to the mode change and the environmental conditions toimprove viewability. This can be a temporary state as the user's eyesadapt to the new operating mode and the associated change in viewingconditions. For example, if the display settings were based on darkerambient conditions than are detected when the head-worn display wakesup, the brightness of the displayed image is modified to match theenvironmental conditions to avoid hurting the user's eyes. In anotherexample, an entertainment mode is used and the brightness of thedisplayed image is slowly increased from the environmental conditions upto level for best viewability of a video with saturated color and highsharpness (Zone 2). In yet another example, if the displayed imageincludes a limited area of icons or white on black text for nighttimeviewing, the brightness is reduced before showing a photo or whitebackground page to account for the increased perception of brightness.

In a yet further embodiment, an eye camera is used to determine whichportion of the displayed image that the user is directly looking at andattributes of the displayed image are adjusted in correspondence to thebrightness of that portion of the displayed image. In this way, theattributes of the image are adjusted in correspondence to the portion ofthe image that the user's eye is reacting to. This approach recognizesthat the human eye adapts very quickly to local changes in brightnesswithin the area that the eye is looking. When the brightness increasesrapidly such as when a light is turned ON in a dark room, the pupildiameter can decrease by 30% in 0.4 sec as shown in studies by Pamplona(Pamplona, V. F., Oliveira, M. M., and Baranoski, G. V. G. 2009,Photorealistic models for pupil light reflex and iridal patterndeformation, ACM Trans. Graph. 28, 4, Articles 106 (August 2009), 12pages). As a result, the user's eye can rapidly adapt to local changesin brightness as the user moves his eye to look at different portions ofthe displayed image or different portions of the see-through view of thesurrounding environment. In order to provide a more consistent perceivedbrightness for different portions of the displayed image, systems ormethods in accordance with the principles of the present inventionadjust the overall brightness of the displayed image in correspondenceto the local brightness of the portion of the displayed image or thelocal brightness of the portion of the see-through view that the user'seye is looking at. In this way, changes in the size of the pupil of theuser's eye are reduced and the user is then provided with a moreconsistent brightness distribution within a displayed image. Wherein theportion of the displayed image or the portion of the see-through viewthat the user's eye is looking at is determined by analyzing images ofthe user's eye that have been captured by the eye camera. The eye cameracan be used in a video mode to capture images of the user's eyecontinuously and the captured images are then analyzed continuously totrack the position of the user's eye over time. The position of theuser's eye within the captured images of the eye is correlated to theportion of the displayed image or the portion of the see-through viewthat the user is looking at. The overall brightness of the displayedimage can then be adjusted in correspondence to the local brightness ofthe portion of the displayed image or the portion of the see-throughview that the user's eye is looking at. The rate of adjustment of theoverall brightness of the displayed image can be further correlated tothe measured diameter of the pupil of the user or to the measured changein diameter of the pupil of the user as determined from analysis of thecaptured images of the user's eye.

In a yet further embodiment, adjustments to attributes of the overallimage can be made based on the local attributes of the portion of thedisplayed image or the portion of the see-through view that the user'seye is looking at. The adjusted attributes of the displayed image caninclude: color, color balance, contrast, sharpness, spatial frequencyand resolution. Where the eye camera is used to capture images of theuser's eye, which are then analyzed to determine the portion of thedisplayed image or the portion of the see-through view that the user'seye is looking at. The portion of the displayed image or the portion ofthe see-through view that the user's eye is looking at is then analyzedto determine the relative intensity of the attribute. Adjustments arethen made to the overall displayed image in correspondence to the localintensity of the attribute in the area that the user's eye is looking atto improve viewability. Where a camera in the head-worn display can beused to capture images of the surrounding environment that at leastpartly correspond to the see-through view provided to the user's eye.

In embodiments, the head-worn computer has an outward facing camera tocapture a scene in front of the person wearing the head-worn computer.The camera and image processing used to determine the area in thesurrounding scene that will be used for brightness and/or colorconsideration in the process of adjusting the displayed content may takea number of forms. For example:

-   -   Camera positioned to capture forward facing scene—the brightness        measure would consider the captured scene and determine a        relevant brightness and/or color. For example, the entire scene        average color/brightness may be considered, a bright or color        saturated portion may be considered, a dark area may be        considered, etc.;    -   The forward facing camera may have a field of view larger than        that of the see-through display's field of view and image        processing may be used to assess the overlapping areas such that        a captured image brightness and/or color may be representative        of the see-through display's field of view brightness and/or        color;    -   The forward facing camera may have a field of view similar to        that of the see-through display's field of view such that a        captured image brightness and/or color may be representative of        the see-through display's field of view brightness and/or color;    -   The forward facing camera may have a narrow field of view to        better target a scene directly in front of the user;    -   The forward facing camera may be a mechanically movable camera        that follows the eye-position (e.g. as determined through        eye-imaging as described herein) to capture a scene that follows        the user's eyes;    -   The forward facing camera may have a wide field of view to        capture the scene. Once the image is captured, a segment of the        image may be identified as being the segment that the user is        looking towards (e.g. in accordance with eye imaging        information) then the brightness and/or color in that segment        may be considered;    -   An object in the captured scene image may be identified (e.g. as        determined based on eye-imaging and position determination) and        the object may be considered; and    -   An object in the captured scene image may be identified as an        object for which the displayed content is going to relate (e.g.        an advertisement to be associated with a store) and the object's        brightness and/or color may be considered.

In a further embodiment, the present invention provides a method forimproving the alignment of a displayed image to the see-through view ofthe surrounding environment. The method can also be used for correlatingeye tracking to where the user is looking in the see-through view of thesurrounding environment. This is an important feature for makingadjustments to attributes in the displayed image when the adjustmentsare based on local attributes in the portion of the see-through viewthat the user is looking at. The adjustment process can be used for eachuser using the head-worn display to improve the viewing experience fordifferent individuals and compensate for variations in eye position orhead shape between individuals. Alternatively, the adjustment processcan be used to fine-tune the viewing experience for a single individualto compensate for different positioning of the head-worn display on theuser head each time the user uses the head-worn display. The method canalso be important for improving the accuracy of positioning of augmentedreality objects. The method includes using an externally facing camerain the head-worn display to capture an image of the surroundingenvironment that includes at least a portion of the user's field of viewof the see-through view of the surrounding environment. A visible markersuch as for example, a cross, is provided in a corner of the capturedimage to provide a first target image. The first target image is thendisplayed to the user so the user simultaneously sees the displayedimage of the surrounding environment from the first target imageoverlaid onto the see-through view of the surrounding environment. Theuser looks at the visible marker and then uses eye tracking control tomove the displayed image to the position where the portion of thedisplayed image adjacent to the visible marker is aligned with objectsin the see-through view of the environment. Where eye tracking controlsinclude an eye camera to determine the movements of the user's eye andblinks of one or both eyes (head movements can be used in conjunctionwith eye controls in the user interface) which are used to in a userinterface to input control inputs. A second image of the surroundingenvironment is then captured and a visible marker is provided in acorner to provide a second target image wherein the visible marker inthe second target image is positioned in a corner that is opposite tothe visible marker in the first target image. The second target image isthen displayed to the user. The user then looks at the visible marker inthe second target and uses eye control to move the displayed image toalign objects in the second target image that are adjacent to thevisible marker with objects in the see-through view of the environment.During the period when the user is viewing the first and second targetimages, it is important that the user not move their head relative tothe environment. The displayed image is then adjusted in correspondencewith the relative amounts that the first and second target images had tobe moved to align portions of the displayed image with correspondingportions of the see-through view of the surrounding environment.

FIG. 127 shows an example of an illustration of a see-through view ofthe surrounding environment with an outline showing the display field ofview 12723 being smaller than the see-through field of view 12722 as istypical.

FIG. 128 shows an illustration of a captured image of the surroundingenvironment which can be a substantially larger field of view than thedisplayed image so that a cropped version of the captured image of theenvironment can be used for the alignment process.

FIG. 129a shows an illustration of a first target image 12928 and FIG.129b shows an illustration of a second target image 12929, wherein thetarget images 12928 and 12929 each include visible markers 12926 and12927 in opposite respective corners.

FIG. 130 shows an illustration of a first target image 12928 overlaidonto a see-through view wherein the first target image 12928 has beenmoved using eye tracking control to align the portion of the firsttarget image that is adjacent to the visible marker 12926 in relation tocorresponding objects in the see-through view. Note that objects in thedisplayed image are shown in FIG. 130 to be smaller in overall sizecompared to the see-through view before being adjusted to improvealignment, but it is also possible that the overall size could be largerbefore adjustment.

FIG. 131 shows an illustration of a second target image 12929 overlaidonto a see-through view wherein the second target image 12929 has beenmoved using eye tracking control to align the portion of the secondtarget image that is adjacent to the visible marker 12927 in relation tocorresponding objects in the see-through view. The movements needed toalign the first target image 12928 and the second target image 12929 arethen used to determine adjustments to the displayed image so that theaccuracy of the alignment of the displayed image field of view 12723with the see-trough field of view 12722 is improved. Where thedetermined adjustments to the displayed image can include adjustments inoverall size, cropping of the image and vertical and horizontal positionof the displayed image within the displayed image field of view 12723.By adding at least one more visible marker to the target images andusing at least one more step to position the target images relative tothe see-through view of the environment, rotational adjustments can bedetermined to further improve the alignment of the displayed image tothe see-through view of the environment. A separate figure showing anillustration of the displayed image sized and aligned to match thesee-through view of the surrounding environment is not shown because itwould look like FIG. 127. The determined adjustments can then be used toimprove the alignment of other displayed images to the see-through viewof the surrounding environment so that areas in the displayed image canbe mapped to the corresponding areas in the see-through view that wouldbe located behind the displayed image when viewed in the head-worndisplay. The determined adjustments can also be used to map themovements of the user's eye to areas in the see-through view of theenvironment as captured in images of the surrounding environment fromthe externally facing camera, so that it can be determined where theuser is looking in the surrounding environment. Further, by analyzing acaptured image of the environment, it can be determined what the user islooking at in the surrounding environment.

In a yet further embodiment, eye tracking controls are used by the userto adjust the size of the displayed image and adjust the position of thedisplayed image to match the see-through view of the surroundingenvironment. In this method, an image of the surrounding environment iscaptured by the externally facing camera in the head-worn display. Theimage of the surrounding environment is then displayed to the userwithin the displayed image field of view 12723 so the usersimultaneously sees the displayed image of the surrounding environmentoverlaid onto the see-through view of the surrounding environment. Theuser then uses eye tracking controls to perform two adjustments to thedisplayed image to improve the alignment of the displayed image of thesurrounding environment with the see-through view of the surroundingenvironment. The first adjustment is to adjust the size of the displayedimage of the surrounding environment in relation to the size of thesee-through view of the surrounding environment. This adjustment can beperformed by the user, for example by a long blink of the eye to beginthe adjustment, followed by a sliding movement of the eye to increase ordecrease the size of the displayed image. Another long blink ends theresizing process. The second adjustment is to position the displayedimage to improve the alignment of the displayed image of the surroundingenvironment with the see-through view of the surrounding environment.This adjustment can be performed by the user for example, by a longblink of the eye to begin the adjustment followed by a slidingdirectional movement of the eye to indicate the movement to align thedisplayed image to the see-through view of the environment. Thisadjustment process can be performed for one eye at a time so that thedisplayed images for the left and right eyes can be positionedindependently for improved viewing of stereo images. The determinedadjustments are then used with other displayed images to improve thealignment of the other displayed images to the see-through view of theenvironment and to determine the mapping of the see-through view as seenbehind the displayed image in the head-worn display. The determinedadjustments can also be used to map the movements of the user's eye toareas in the see-through view of the environment as captured in imagesof the surrounding environment from the externally facing camera, sothat it can be determined where the user is looking in the surroundingenvironment. Further, by analyzing a captured image of the environment,it can be determined what the user is looking at in the surroundingenvironment.

While some of the embodiments above have been described in connectionwith the use of eye tracking input for display content control andadjustment, it should be understood that an external user interface maybe used in conjunction with or instead of eye-tracking control. Forexample, when the displayed content is presented in the field of view ofthe head-worn display, a touch pad, joy stick, button arrangement, etc.may be used to align the content with the surrounding environment.

In embodiments, the displayed content may be color adjusted depending onthe scene background that will be behind the displayed content in thesee-through display to compensate for the color of the scene backgroundsuch that the displayed content appears to be properly color balanced.For example, if the scene background over which the displayed contentwill be overlaid is red (e.g. a red brick wall), the displayed contentmay be adjusted to reduce its red content because some of the scene'sred content will be seen through the displayed content and hencecontribute to the red content in the displayed content.

In embodiments, the displayed content may be adjusted as describedherein (e.g. to blend or be distinguished from the scene as viewedthrough the see-through display) by adjusting a color and/or intensityof light produced by a lighting system adapted to light a reflectivedisplay, adjusting the image content through software image processing,adjusting an intensity of one or more colors of an emissive display,etc.

In embodiments, the see-through scene brightness and/or color may bebased on an average see-through brightness and/or color of the scene asviewed through the display or otherwise proximate the head-worn display,a brightness and/or color of an object apparently in view through thesee-through display, an eye heading (e.g. eye position based on eyeimaging as described herein), compass heading, etc.

The inventors have discovered that, in head-worn displays that includemultiply folded optics, it can be advantageous to use a solid prism withan included fold surface to improve image quality and enable a morecompact form factor. They have also discovered that manufacturing of thesolid prism by molding can be challenging due to sink marks, which oftenappear on planar surfaces. In addition, providing the illumination lightinto the solid prism at the required angle requires specialconsiderations. Imaging of the user's eye can be an important feature inhead-worn displays for user identification and as a user interface. Eyeimaging apparatus are provided herein for a variety of head-worndisplays.

An aspect of the present invention relates to a solid prism withimproved manufacturability along with design modifications that enableillumination light to be effectively supplied into the solid prism atthe required angle to illuminate the image source.

An aspect of the present invention relates to a solid prism with a foldsurface platform, wherein an optically flat fold surface is mounted onthe prism's fold surface platform such that the fold surface maintains ahigh optical flatness that minimizes aberrations in the prism's foldsurface platform.

An aspect of the present invention relates to providing additionaloptical features in the solid prism that are used for capturing imagesof the user's eye with an eye imaging camera.

An aspect of the present invention relates to providing a solid prismwith a fold surface, wherein the solid prism includes shaped inputand/or output surfaces that act as optical power producing opticalsystems.

An aspect of the present invention relates to a solid prism with opticalpower producing surfaces with an additional power lens above thecombiner such that the physical size of the power lens above thecombiner is reduced thereby reducing the overall size of the opticalsystem.

An aspect of the present invention relates to a solid prism with anoptically powered surface at the image light-receiving end of theoptical path from the display, wherein an additional optically poweredfield lens is positioned between the display and the optically poweredsurface to further increase the optical power of the optical system.

An aspect of the present invention relates to a solid prism with a foldsurface that includes optically powered input and/or output surfaces andmaterial selection amongst related optical materials that are adapted toreduce lateral color aberrations and thereby improve image qualityprovided to the user.

An aspect of the present invention relates to an angled backlightassembly that redirects illumination light toward an image sourcethrough the inclusion of a prism film, wherein the prism is positionedon the side of the backlight so that it acts like a Fresnel wedge.

An aspect of the present invention relates to a stray light managementsystem adapted to manage stray light produced by a prism film used in abacklighting system, wherein the prism film causes significant straylight and an analyzer polarizer film is positioned in an image lightoptical path to absorb such stray light.

An aspect of the invention relates to an emissive display system thatprojects image light into a solid prism with a fold surface for deliveryof the image light to the user's eye.

An aspect of the present invention relates to projecting illuminatinglight through a portion of the display optics and towards a combinersurface, wherein the illuminating light reflects off the combinersurface and directly towards an eye of the user to thereby illuminatethe eye for eye imaging. In embodiments, the display optics includes asolid prism and a light source is mounted above the fold surface of thesolid prism.

An aspect of the present invention relates to capturing eye imagesdirectly from the combiner, wherein the eye-imaging camera is mountedabove the combiner. In embodiments, an eye light is positioned at thetop edge of the combiner so the eye is illuminated directly.

An aspect of the present invention relates to a surface applied to thecombiner, wherein the surface is applied outside of the field of view ofthe see-through display and adapted to reduce stray light reflectionsfrom reflecting off the combiner and towards an eye of the user.

An aspect of the present invention relates to a surface applied to thecombiner, wherein the surface is adapted to reflect infrared light andpass visible light such that visible stray light reflections towards theuser's eye are minimized and such that infrared light from an infraredlight source is reflected towards the user's eye. The infraredreflections may then be used for eye imaging.

An aspect of the present invention relates to eye imaging through awaveguide optic adapted to transmit image light and to be see-throughfor a user's view of the surroundings, wherein the eye imaging camera ispositioned to receive eye images through the waveguide optic such thatthe image is captured from a position in front of the user's eye.

An aspect of the present invention relates to eye imaging by capturingreflected light off of an outer surface of a waveguide optic adapted totransmit image light and to be see-through for a user's view of thesurroundings.

FIG. 132 shows an illustration of multiply folded optics for a head worndisplay that includes a solid prism 13250. Where the solid prism 13250includes a planar surface 13254 (i.e. a first fold surface) that isreflective to redirect the image light 13230 and thereby provide a firstfold to the optical axis 13235 to enable the multiply folded optics tobe more compact than optics which do not include this fold. As shown inFIG. 132, a second fold of the optical axis 13235 is provided in thelower portion of the multiply folded optics where the image light 13230is reflected by the combiner 13210 (i.e. a second fold surface) so theimage light 13230 is directed into the eyebox 13220 where the user's eyeis located as has been previously described herein. The planar surface13254 can be a full mirror so that all of the image light 13230 isreflected, wherein the image source 13260 must be a self-luminous imagesource such as an OLED or a backlit image source such as an LCD so thatthe image light 13230 is provided directly by the image source 13260.However if the image source 13260 is a reflective image source such as aLCOS, FLCOS or DLP illumination light must be supplied which is thenreflected by the image source 13260 to provide image light 13230. In thecase where the reflective image source is an LCOS or FLCOS, whereillumination light is needed at a high incidence angle, the planarsurface 13254 can be a partial mirror so that illumination light can beprovided from a light source located behind the planar surface 13254 andpointed at the image source 13260. In the case where the reflectiveimage source is a DLP, where illumination light is needed at an anglecommensurate with the mirror angles, the planar surface 13254 may beextended, or an additional surface may be provided, such that light canbe provided from a light source located behind the planar surface 13254or the additional surface. In embodiments, a first advantage provided bythe solid prism 13250 is that the cone angle of the image light 13230 isreduced inside the solid prism 13250 thereby extending the optical pathlength so that a fold can be provided to the optical axis 13235 therebyenabling a more compact size of the multiply folded optics. A secondadvantage of the solid prism 13250 is that the planar surface 13254provides an internal reflection so that dust cannot collect on thereflective surface. A third advantage of the solid prism 13250 is thatstray light is easier to control by blackening the external surfacesthat do not need to transmit light.

In addition to folding the optical axis 13235 by reflecting off theplanar surface 13254, the solid prism 13250 can also provide opticalpower since the input and output surfaces 13252 can be curved. FIG. 132shows two surfaces 13252 that have optical power. By providing some ofthe optical power needed in the multiply folded optics, the power lens13240 doesn't need to provide as much optical power and as a result, thepower lens 13240 is thinner and the overall size of the multiply foldedoptics is thereby reduced. A field lens 13270 can also be provided toact in conjunction with the solid prism 13250 and the power lens 13240.By selecting the materials of the field lens 13270, the solid prism13250 and the power lens 13240 to be different in terms of refractiveindex and Abbe number (combining flint and crown glass properties as isknown by those skilled in the art), the lateral color aberration in theimage light 13230 provided to the eyebox 13220 can be substantiallyreduced thereby improving the sharpness of the image as perceived by theuser particularly in the corners of the image.

In the multiply folded optics, the surfaces (13254 and 13210) that foldthe optical axis 13235 are preferentially optically flat (e.g. flatnessbetter than 10 microns) to maintain the wavefront of the image light13230 and thereby provide a high quality image to the user. Thesesurfaces can be tilted relative to the optical axis 13235 to compensatefor twists of the upper portion of the optics (extending from the imagesource 13260 to the bottom surface of the solid prism) relative to thelower portion of the optics (extending from the power lens to theeyebox) as has been described previously herein.

Manufacturing of a plastic solid prism 13250 by molding can bedifficult, because the solid prism 13250 has non-uniform thickness andit can include curved surfaces and flat surfaces. Injection molding ofcurved surfaces requires a different process setup than that requiredfor injection molding flat surfaces. In particular, optically flatsurfaces can be very difficult to injection mold without sink marks whenthe thickness of plastic under the flat surface is not uniform as is thecase for the solid prism 13250. To overcome this difficulty, the presentdisclosure provides a separate reflective plate 13275 that is used toestablish an improved flat surface 13254. The reflective plate 13275 canbe manufactured using a sheet manufacturing process so that a highdegree of optical flatness is provided. In a preferred embodiment, thereflective plate 13275 is a glass plate that has been coated to providereflectivity. Where the coating can be a full mirror if the image source13260 is a self-luminous display or it can be a partial mirror if theimage source 13260 is a reflective display. In a further preferredembodiment, the reflective plate 13275 includes a glass plate with areflective polarizer such as a Proflux wire grid polarizer by Moxtek(Orem, Utah) so that light of one polarization state is reflected andlight of the opposite polarization state is transmitted.

The reflective plate 13275 can be bonded to the planar surface 13254 ofthe solid prism 13250 using a transparent adhesive that has a refractiveindex that is very similar (within for example +/−0.05) to that of thesolid prism material (also known as index matched). By matching therefractive index of the adhesive to the refractive index of the solidprism 13250, the interface between the solid prism material and theadhesive becomes optically invisible. In this way, the adhesive can fillin any spaces between the reflective plate 13275 and the planar surface13254 of the solid prism 13250 that are caused by sink marks, scratches,grooves or other non-flatness of the planar surface of the solid prism.The flatness of the planar surface as molded on the solid prism 13250 isthen not important to the optical performance of the multiply foldedoptic, and instead the flatness of the reflective plate 13275 determinesthe a new flat surface 13254 with improved flatness. In this way, themanufacturing of the solid prism 13250 becomes easier and less expensivebecause the planar surface 13254 does not have to be an optically flatsurface as molded (or otherwise manufactured) and the manufacturingprocess used to make the solid prism 13250 can be optimized for thepowered surfaces 13252. In addition, by bonding the reflective surfaceof the reflective plate 13275 to the planar surface 13254, the opticallyflat reflective surface is protected from being damaged during thefurther assembly process of the multiply folded optics.

FIGS. 133a, 133b and 133c show illustrations of steps associated withbonding the reflective plate 13275 to the solid prism 13250. As shown inFIG. 133a , the solid prism 13250 is mounted for bonding so that theplanar surface 13254 is approximately horizontal. A drop 13377 ofrelatively low viscosity (e.g. 200 centipoise) transparent adhesive isthen applied to the flat surface 13254. Where the adhesive is selectedto have a refractive index that is very similar to the material of thesolid prism 13250 so that the adhesive and the solid prism are indexmatched. The reflective plate 13275 is then brought into contact withthe drop 13377 as shown in FIG. 133b . The adhesive is then allowed towick across the interface between the reflective plate 13275 and theplanar surface 13254 until the entire interface is covered by theadhesive as shown in FIG. 133c . Importantly, in embodiments, nopressure is applied to the reflective plate 13275 during the bondingprocess so that the reflective plate 13275 is not distorted and theoptical flatness of the reflective plate 13275 is maintained. The drop13377 used is relatively small so the interface is covered withoutadhesive oozing out at the edges. The adhesive is then cured, by waitingthe appropriate length of time, applying heat or applying UV light asappropriate for the adhesive. In a preferred embodiment, a UV curingadhesive is used to provide a rapid cure. The advantage of bonding thereflective plate 13275 to the solid prism 13250 is that the adhesive canfill any sink marks that may be present on the planar surface of theprism so that the surface of the reflective plate 13275 establishes aplanar surface 13254 with improved flatness and a desired level ofreflectivity to reflect the image light 13230. Since the adhesive isindex matched to the material of the solid prism 13250 the image light13230 passes from the solid prism 13250 through the layer of adhesive tothe surface of the reflective plate 13275 without disturbing thewavefront of the image light 13230 so that high image quality ismaintained.

FIG. 134 shows an illustration of multiply folded optics for areflective image source with a backlight assembly positioned behind thereflective plate 13275. Where, as shown in FIG. 134, the reflectiveplate 13275 is a partial mirror that transmits at least a portion of thelight from the backlight to illuminate the image source 13260 and thenreflects at least a portion of the image light 13230. In a preferredembodiment, the reflective plate 13275 is a reflective polarizer thattransmits one polarization state while reflecting the oppositepolarization state. In this case, the illumination light 13432 isprovided with a first polarization state (for example P polarization)and the image light 13230 is a second polarization state (for example Spolarization). This change in polarization state occurs in the brightareas of the displayed image when the illumination light 13432 isreflected by the image source 13260 if the image source 13260 is forexample a normally white LCOS. As a result, image light 13230 in thebright areas of the displayed image are reflected by the reflectivepolarizer of the reflective plate 13275 and image light in the darkareas of the displayed image is transmitted by the reflective polarizer,so that image light of only the second polarization state passes intothe lens 13240. The backlight assembly includes a prism film 13477 todeflect, at least a portion of the illumination light 13432 provided bythe light guide 13480, toward the image source 13260. Where the prismfilm 13477 can be a turning film such as DTF provided by LuminitCorporation (Torrance, Calif.) or alternatively the prism film can be abrightness enhancement film such as Vikuiti BEF4-GT-90 provided by 3M(St. Paul, Minn.). A diffuser film 13478 is also included in thebacklight assembly to provide the desired cone angle of light within theillumination light 13432. A light source 13479 is also included in thebacklight assembly to provide light to the light guide 13480, where thelight source 13479 can be one or more LEDs. The light source 13479 canprovide white light or sequential color illumination (e.g. a repeatingsequence of red then blue then green illumination, or cyan then magentathen yellow illumination) depending on whether the reflective imagesource includes a color filter array or not.

In a solid prism 13250, the angle that the illumination light 13432 canbe provided at is limited by refraction effects at the interface wherethe light enters the solid prism 13250. As an example, following Snell'slaw for refraction across an interface

n1 sin θ1=n2 sin θ2

to provide illumination light 13432 inside the solid prism with theapproximately 30 degree angle from the interface normal that is shown inFIG. 134, the light from the backlight assembly would have to beprovided to the interface at approximately 50 degrees if the prismmaterial has a refractive index of 1.5. Where n1 is the refractive indexof the first medium where the light is coming from 81 is the angle ofthe light relative to the surface normal in the first medium, n2 is therefractive index of the second medium where the light is going and 82 isthe angle of the light relative to the surface normal in the secondmedium. Providing illumination light 13432 with a 50 degree angle fromthe backlight assembly can be difficult as turning films are notavailable that deflect light by such a large angle. To reduce refractioneffects, a prism film 13477 is used as a Fresnel wedge with the smoothside bonded to the reflective plate 13275 and the prism structurepointed toward the backlight assembly. FIG. 135 shows an illustration ofa prism film 13477 bonded to a reflective plate 13275, where the prismfilm 13477 shown is a brightness enhancement film with linear prismaticsurfaces oriented at approximately 45 degrees to the interface (therebyforming linear prisms with a 90 degree included angle) and an opticallyclear adhesive 13578 such as 8142KCL available from 3M (St. Paul, Minn.)used to bond the prism film 13477 to the reflective plate 13275. Itshould be noted that this orientation with the prismatic structurepointed toward the light source is opposite to the orientation typicallyused for a brightness enhancement film, which is typically used tocollimate light in a backlight. Instead, with the orientation shown inFIG. 135, following Snell's Law as previously described herein, the 45degree surfaces of the brightness enhancement film split the incominglight into two cones of light (illustrated in FIG. 135a as light 13532and 13533) with respective deflection angles of approximately +/−17degrees inside the prism film 13477 relative to the incidentillumination light from the diffuser which is approximatelyperpendicular to the plane of the light guide 13480 and the plane of thereflective plate 13275. Importantly, the prism film provides asubstantially reduced amount of light between the two cones of light.Where the cone angle of the light within each of the cones of light isdetermined by the cone angle of the diffuser 13478. The deflection angleof the illumination light 13432 can be modified by adding a turning film(not shown) on top of the prism film, where the turning film changes theangle of the illumination light provided to the prism film 13477.Typical turning film such as the DTF film available from Luminit(Torrance, Calif.) provides a 20 degree deflection of light. Theillumination light is then incident onto one surface of the prism filmat 65 degrees and 25 degrees on the other surface of the prism film. Thetwo cones of illumination light inside the prism film have deflectionangles of +28 and −8 degrees relative to the incident illumination lightfrom the diffuser which is approximately perpendicular to the plane ofthe light guide 13480 and the plane of the reflective plate 13275. Sincethe prism film 13477 is bonded to the reflective plate 13275 and thereflective plate is bonded to the solid prism 13250, the angle of lightinside the prism film 13477 is essentially maintained into the solidprism 13250, provided the refractive indices of the prism film 13477,the reflective plate 13275 and the solid prism 13250 are reasonablysimilar. In this way, the system deflects the illumination light 13432provided by the backlight assembly in a direction that directs theillumination light 13432 toward the image source 13260. The image source13260 is thereby illuminated by the light guide 13480 in a way thatallows the multiply folded optics to have a more compact form factor asprovided by the multiple folds of the optical axis 13235. Inmanufacturing, the prism film 13477 can be bonded to the reflectiveplate 13275 either before or after the reflective plate 13275 is bondedto the solid prism 13250.

FIG. 135a shows an illustration of multiply folded optics in which thetwo cones of illumination light 13532 and 13533 provided by the prismfilm 13477 are shown. While illumination light D32 illuminates the imagesource 13260, illumination light 13533 is a form of stray light in themultiply folded optics that must be controlled to provide high contrastimage light 13230 to the eyebox 13220 so that the user experiences ahigh contrast image. The advantage provided by the prism film 13477 isthat approximately half of the illumination light (13532) is deflectedtoward the image source 13260 while the other half of the illuminationlight (13533) is deflected in a direction where stray light can becontrolled and little light is provided between 13532 and 13533 wherecontrol of stray light is more difficult. FIG. 135a includes an analyzerpolarizer 13582 to absorb the portion of light 13533 from the backlightthat is not used to illuminate the image source 13260. Analyzerpolarizer 13582 is shown positioned between the power lens 13240 and thecombiner 13210, however, the analyzer polarizer 13582 could also bepositioned in the gap between the solid prism 13250 and the power lens13240. The analyzer polarizer 13582 is oriented with its transmissionaxis so that light with the polarization state of the bright areas ofthe image light is transmitted and light with the polarization state ofthe dark areas of the image light and the illumination light 13533 isabsorbed. As such, the analyzer polarizer provides a dual purpose byreducing stray light associated with the illumination light 13533 andassociated with image light in the dark areas of the image.

In multiply folded optics with a solid prism, additional opticalelements can be added for imaging the eye of the user for the purpose ofeye tracking in a user interface or eye identification for securitypurposes. FIGS. 136, 137 and 138 show illustrations of differentembodiments of additional optical elements included in the solid prismfor imaging the eye of the user. FIGS. 136 and 137 show illustrations ofvarious views of an optical element 13612 attached to the side of thesolid prism 13250 such that eye camera 13610 can image the user's eye inthe eyebox 13220. The optical element 13612 is shown as a single lenssurface angled relative to optical axis 13235 to provide a field of viewthat includes light 13613 reflected from the user's eye. In this way,the light 13613 reflected from the user's eye is multiply folded in away that is similar to the image light 13230. However, the opticalelement 13612 can include more than one lens surface and more than onelens element to improve the resolution of the eye imaging. FIG. 137shows how the optical element 13612 can be positioned adjacent tosurfaces 13252 on the solid prism 13250. With the optical element 13612positioned as shown in FIGS. 136 and 137, the eye camera 13610 isprovided with a field of view that includes light 13613 reflected by theeye and the field of view associated with the optical element 13612tends to extend to the upper portion of the user's eye. Where the user'seye can be passively illuminated by image light 13230 or activelyilluminated by additional lights (not shown) adjacent to the eyebox13220 or adjacent to the optical element 13612. The additional lightscan be infrared lights provided the eye camera 13610 can captureinfrared images of the user's eye. FIG. 138 shows an illustration ofanother solid prism 13250 with an optical element 13812 positionedadjacent to the top of the solid prism 13250 to enable the eye camera13814 to image the eyebox 13220. In this case, the optical element 13812is attached to the solid prism 132450 and designed to provide a field ofview that includes light 13813 that is reflected from the user's eye.The light 13613 is reflected by the user's eye and captured by the eyecamera 13814 following a singly folded path. Where the field of viewassociated with the optical element 13812 being positioned as shown inFIG. 138 tends to extend to the side of the user's eye. In both of theembodiments shown for eye imaging in FIGS. 136, 137 and 138, the opticalelements 13612 and 13812 are designed to take into account the fact thatthe light reflected by the user's eye passes through the power lens13240 and at least a portion of the solid prism 13250. From amanufacturing perspective, the optical elements 13612 and 13812 can bemade as attachments to the solid prism 13250 or made as an integral partof the solid prism 13250 that is molded along with the other surfaces ofthe solid prism 13250.

In a further embodiment, eye imaging is included for the multiply foldedoptics shown in FIG. 132. FIG. 139 shows an illustration of an eyeimaging system for multiply folded optics in which the image source is aself-luminous display such as for example an OLED or a backlit LCD. Inthis case, the reflective plate 13275 is a partial mirror that is bondedto the planar surface 13254 of the solid prism 13250 as previouslydescribed herein. Alternatively a partial mirror coating can be applieddirectly to the planar surface 13254, provided the planar surface 13254is optically flat. The partial mirror then reflects a portion of theimage light 13230 thereby redirecting it toward the lens 13240 and thecombiner 13210 where the image light 13230 is reflected a second timeand thereby redirected toward the user's eye to provide an image to theeyebox 13220. Simultaneously, a portion of the light 13923 reflected bythe user's eye is transmitted by the partial mirror and captured by aneye camera 13922. Where, the user's eye can be passively illuminated bythe image light 13230 and additional active illuminating light 13913 canbe provided by an eye light 13912 to illuminate the user's eye. In apreferred embodiment, the eye light 13912 provides infrared illuminatinglight 13913 and the eye camera 13922 is sensitive to infrared light, inthis way the illuminating light 13913 doesn't interfere with the imagesdisplayed to the user by the image light 13230. In a further preferredembodiment, the partial mirror is a cold mirror that reflects a majorityof visible light (e.g. greater than 80% of visible light, 400-700 nm)and transmits a majority of infrared light (e.g. greater than 80% ofinfrared light 800-1000 nm). In a yet further preferred embodiment, thecombiner is at least partially coated with a hot mirror coating thatreflects infrared light and transmits visible light. Wherein forexample, the hot mirror coating can reflect greater than 80% of theinfrared light provided by the eye light and transmit greater than 50%of the visible light associated the see-through view of the surroundingenvironment. By including a cold mirror on the planar surface or thereflective plate 13275 along with a hot mirror on the combiner 13210,losses of the light 13923 reflected by the user's eye can be reducedthereby enabling bright images to be captured of the user's eye andreducing power needed for active illumination of the user's eye by theeye light 13912.

FIGS. 140a and 140b show illustrations of folded optics with a combiner14010 that redirects image light 13230 that has been provided by upperoptics 1406 that includes an image source and associated optics. Acamera 14022 is provided for imaging the user's eye 140B when positionedadjacent to the eyebox 13220. An eye light 14012 is provided to provideilluminating light 14013 that is reflected by the combiner 14010 andthereby directed toward the user's eye 1408. Where, the camera 14022 ispositioned to one side of the upper optics 1406 so that light 14023reflected by the user's eye is reflected by the combiner 14010 andcaptured by the camera 14022. As previously described herein, the eyelight 14012 can provide infrared illuminating light 14013 (e.g. 850 nm)and the combiner 13220 can include a hot mirror coating to reflect themajority of the infrared illuminating light 14013, while providing asee-through view of the surrounding environment. The eye light 14012 canbe positioned to one side of the upper optics 1406 and preferably theeye light 14012 is positioned adjacent to the camera 14022 so that theilluminating light 14013 causes light 14023 to be reflected from theuser's eye with a distribution that can be efficiently captured by thecamera 14022. For example, the eye light 14012 can be positioned on anadjacent side of the upper optics 1406, as in FIGS. 140a and 140b wherethe eye light 14012 is shown positioned on the back side of the upperoptics 1406 so the illuminating light is reflected by the combiner backtoward the user's eye 140 b and the camera 14022 is shown on the leftside of the upper optics 1406, but other arrangements are also possible.In a preferred embodiment, the eye light 14012 is a small LED that ismounted on the lower front edge of the upper optics 1406 and pointeddirectly back toward the user's eye 1408.

In embodiments, the combiner 14010 includes a surface that preventsvisible light reflections outside of the field of view. The surface mayinclude an anti-reflective coating and it may only be applied outside ofthe field of view. This arrangement can be useful in preventingenvironmental stray light from reflecting into the user's eyes. Withoutsuch a surface, light from the environment may reflect off of thecombiner surface and into the user's eye.

FIGS. 141a and 141b show illustrations of folded optics that include awaveguide 14132 with an angled partially reflective surface 14135 and apowered reflective surface 14136. Where an image source 14153 providesimage light 14130 that is reflected by reflective plate 14175 so thatthe image light 14130 is conveyed by the waveguide 14132 to thepartially reflective surface 14135 where it is transmitted to thepowered reflective surface 14136 where it is condensed and reflectedback toward the partially reflective surface 14135. The partiallyreflective surface then reflects and redirects the image light so thatthe image light 14130 is provided to the user's eye 1408. In theembodiment shown in FIG. 141a , an eye light 14112 is positionedadjacent to one end of the waveguide 14132 so that illuminating light14113 is directed at the user's eye 1408. A camera 14122 is positionedbehind the reflective plate 14175 wherein the reflective plate reflectsat least a portion of the image light 14130 and transmits at least aportion of the light 14123 that is reflected by the user's eye 1408.Wherein the reflective plate 14175 can be a partially reflecting mirror,a reflective polarizer or in a preferred embodiment the reflective plate14175 is a cold mirror that reflects visible light and transmitsinfrared light (e.g. the cold mirror reflects greater than 80% ofvisible light, 400 to 700 nm, and transmits greater than 80% of theinfrared light provided by the eye light, 800 to 1000 nm). It will benoted that in some cases the reflective plate can be replaced by acoating applied directly to the underlying planar surface of thewaveguide 14132 provided the planar surface is optically flat. Aspreviously described herein, eye light 14112 can provide infraredilluminating light 14113 provided the camera 14122 is sensitive toinfrared. By positioning the camera 14122 behind the angled reflectiveplate 14175, the image light 14130 and the light 14123 reflected by theuser's eye 1408 can be coaxial so that images captured of the user's eye1408 are from a perspective directly in front of the user. FIG. 141bshows another embodiment in which the eye light 14112 is positionedadjacent to the camera 14122 so that the illuminating light 14113 istransmitted by the reflective plate 14175 and conveyed by the waveguide14132 in a manner similar to the image light 14130 so that it isredirected toward the user's eye 1408.

FIGS. 142a and 142b show illustrations of folded optics for a head-worndisplay that include waveguides 14232 with at least one holographicoptical element 14242 and image source 14253. In this embodiment, theimage source 14253 provides image light 14230 to the waveguide 14232(not shown) so that the holographic optical element 14242 can redirectthe image light 14230 at approximately 90 degrees towards the user's eye1408. A camera 14222 is provided to capture images of the user's eye1408. An eye light 14212 provides illumination light 14213 to the user'seye 1408. Light 14223 is reflected by the user's eye 1408 and iscaptured by the camera 14222. As shown in FIG. 142a , the eye light14212 is positioned to one side of the waveguide 14232 and adjacent tothe camera 14222. A hot mirror coating with its reflection spectrummatched to the infrared spectrum provided by the eye light 14212, isapplied to at least a portion 14224 of the waveguide 14232 so that themajority of light 14223 is reflected toward the camera 14222 and abright see-through view of the surrounding environment is providedsimultaneously. FIG. 142b shows an illustration of similar folded opticsfor a head-worn display in which the waveguide 14232 is positioned at anangle to the user's eye 1408 to provide a closer fit of the foldedoptics to the user's head. In this case the holographic optical element14242 is designed to redirect the image light 14230 at approximately 110degrees to the waveguide and towards the user's eye 1408. The camera14222 is then positioned at the end of the waveguide 14232 that isopposite to the image source 14253 to enable the angle between the light14223 reflected from the user's eye 1408 and the illumination light14213 to be reduced. In this way an image of the user's eye 1408 withmore uniform brightness can be captured by the camera 14222. Aspreviously described herein, at least a portion 14224 of the waveguide14232 can be a hot mirror to reflect a majority of the light 14223reflected by the user's eye 1408 while a bright see-through view of thesurrounding environment is provided simultaneously.

FIG. 143 shows an illustration of folded optics for a head-worn displayin which the illumination light is injected into the waveguide andredirected by the holographic optical element so that the user's eye isilluminated. Eye light 14312 is positioned at one end of the waveguide14232 so that the illumination light 14313 can be injected into thewaveguide 14232 and conveyed along with the image light 14230 to theholographic optical element 14242. The holographic optical element 14242then redirects the image light 14230 and the illumination light 14313towards the user's eye 1408. The holographic optical element 14242 mustthen be capable of redirecting both the image light 14230 and theillumination light 14313, where the image light 14230 is visible lightand the illumination light 14313 can be infrared light. Light 14223reflected by the user's eye is then reflected by the waveguide surfaceand captured by the camera 14222. A hot mirror coating with itsreflection spectrum matched to the infrared spectrum provided by the eyelight 14212, is applied to at least a portion 14224 of the waveguide14232 so that the majority of light 14223 is reflected toward the camera14222 and a bright see-through view of the surrounding environment isprovided simultaneously. The advantage of this design is that theillumination lighting system including eye light 14312 can be made morecompact. FIG. 144 shows an illustration of folded optics for a head-worndisplay that is similar to the system shown in FIG. 143 where a seriesof angled partial mirrors 14442 are included in the waveguide instead ofa holographic optical element. In this case, illumination light 14413 isinjected into the waveguide 14432 along with image light 14230 providedby the image source 14253. The illumination light 14413 and the imagelight 14230 are conveyed by the waveguide 14432 to the series of angledpartial mirrors 14442 which redirect the illumination light 14413 andimage light 14230 towards the user's eye 1408. Light 14223 reflected bythe user's eye 1408 is reflected by a hot mirror coating applied atleast to a portion 14224 of the waveguide 14432 wherein the reflectionspectrum of the hot mirror is matched to the infrared spectrum of theillumination light 14413 provided by the eye light 14212. The advantageof this design is that the illumination lighting system is compact andthe series of angled partial mirrors can be easily made to operate onboth the visible image light 14230 and the infrared illumination light14413.

When using a head-worn display for augmented reality applications,particularly when the head-worn display provides a see-through view ofthe surrounding environment, it can be important to be able to changethe focus depth that the displayed image is presented at. It is alsoimportant to present stereo images at the proper vergence distance toprovide the intended perception of depth to the user. Where focusdistance is the distance the user's eye must be focused at to view asharp image and vergence distance is the distance the user's two eyescome together to view the same spot in an image or on a real object.Within a stereo image, objects intended to be perceived to be atdifferent depths are presented with a rendered lateral shift between therelative locations of the object within the left and right images, whichis known as disparity. The rendering of typical stereo imagery as viewedin theaters or on televisions is mostly directed at disparity mapping ofobjects to create the 3D effect because the focus distance is limited tothe theater screen or television (see the paper “Nonlinear disparitymapping for stereoscopic 3D”, M. Lang, A. Hornung, O. Wang, S. Poulakos,A. Smolic, M. Gross, ACM Transactions on Graphics (Impact Factor: 3.73).August 2010; 29. DOI: 10.1145/1833349.1778812). To make the stereoviewing experience more comfortable for the user, the vergence distanceassociated with viewing an augmented reality object should closely matchthe focus distance associated with the same augmented reality objectthereby enabling the augmented reality object to more closely resemble areal object as seen by the user of the head-worn display. The systemsand methods in accordance with the principles of the present inventionprovide methods of changing the focus distance and vergence distanceassociated with augmented reality objects and imagery viewed in ahead-worn display in ways that more closely match real objects in asee-through view of the surrounding environment.

The focus distance of an image displayed in any head-worn display isdetermined by the elements in the optics of the head-worn display. Thefocus distance of the image can be changed by changing the elements inthe optics, or by changing the relative positioning of some of theelements in the optics. The vergence distance associated with stereoimages is determined by the lateral positioning of the images within thefield of view of the user's left and right eyes. The vergence distancecan be changed by laterally shifting the left and right images relativeto one another within the user's fields of view either by repointing theleft and right optics thereby establishing a different point ofconvergence between the left and right optics or by digitally shiftingthe displayed images within the display fields of view. To provide astereo viewing experience of augmented reality objects that more closelyresemble the viewing experience associated with a real object, it isimportant that the focus distance match the vergence distance foraugmented reality objects in displayed stereo images in a head-worndisplay within the limitations of the user's eyes. Given that augmentedreality objects are often positioned at different distances withinstereo images and as different augmented reality activities areconducted at different distances, the inventors have discovered thatmethods are needed to change focus distance with a corresponding changein vergence distance within all types of head-worn displays.

FIG. 145 shows an illustration of a beam splitter based optical modulefor a head-worn display (shown from the side and from the eye position)that includes upper optics 14510 and a combiner 14520. Wherein the upperoptics 14510 include an image source, a light source and one or morelens elements. The combiner 14520 is a beam splitter that reflects aportion of the image light associated with the displayed image towardthe user's eye while also allowing light from the surroundingenvironment to be transmitted so that the user sees the displayed imageoverlaid onto a see-through view of the surrounding environment. FIG.146 shows an illustration of an optical module for a head-worn display(also shown from the side and from the eye position) that has beenmodified to change the focus distance by adding a focus shift element14625. Where the focus shift element 14625 is a thin lens with opticalpower. For example, the focus shift element 14625 required to change thefocus distance from infinity to 1 meter needs to provide −1 diopter ofoptical power. As such the focus shift element 14625 can be a refractivelens such as a portion of an ophthalmic lens, which is 1 to 1.5 mmthick. Alternatively, the focus shift element 14625 can be a Fresnellens, which can he thinner than a refractive lens. By positioning thefocus shift element 14625 above the combiner 14520, the optical power ofthe focus shift element 14625 only acts on the displayed image and doesnot change the see-through view of the surrounding environment. Thismethod can be used in any type of optics for a head-worn display (e.g.projected optics with a see-through combiner, holographic imageprojection with a see-through combiner, see-through optics with asee-through waveguide, TIR wave guide, etc.) wherein space is availableto insert a focus shift element with optical power into the optical pathsuch that the focus distance is changed without changing the see-throughview. In the event that the upper optics 14510 utilize polarized imagelight, a polarization control element 14515 can be included to modifythe polarization state of the image light. Where the polarizationcontrol element can include one or more of the following: a polarizer tocut unwanted polarization states, a retarder such as a quarter wave filmto change the image light to circularly polarized or a half wave film tochange the polarization state.

For the case where the user's eyes are not capable of focusing at thefocus distance associated with the displayed image, a corrective lenselement can be provided behind the optics module to improve thesharpness of the displayed image as perceived by the user. In this case,the corrective lens element is based on the user's ophthalmicprescription and the corrective lens element improves the view for theuser of both the displayed image and the see-through view of thesurrounding environment. FIG. 146a shows an illustration of a side viewof an optics module that includes a corrective lens element 14624. Thecorrective lens element 14624 can have a positive optical power or anegative optical power as required by the user for viewing the displayedimage at the focus distance. In addition, the corrective lens elementcan also include astigmatism and wedge as included in the user'sophthalmic prescription. Corrective lens elements 14624 for the left andright eyes can be connected to each other to provide a corrective unitthat is attached and aligned to the optics module or frame of thehead-worn display with either a built-in interpupillary spacing or aflexible interpupillary spacing. Alternatively, the left and rightcorrective lens elements 14624 can be separate and be attached andaligned individually to the optics module or frame of the head-worndisplay. For example, for applications where the displayed image ispresented with a focus distance and vergence distance of 0.6 meters sothat augmented reality objects or information can be provided for a taskperformed at arm's length, the focus shift element 14625 could have anoptical power of −1.6 diopter and could provide only optical power andthe corrective lens element 14624 could have an optical power of +2diopters and also provide correction for astigmatism and wedge per theuser's ophthalmic prescription. Where a +2 diopter corrective lenselement 14624 would be a fairly typical prescription for reading glassesfor a person of approximately 55 years old and as such would enable theperson to view objects and images clearly that are positioned at arm'slength. The corrective lens element 14624 shown in FIG. 146a is arefractive lens, but other types of lenses are also possible, such asFresnel lenses.

While lenses with fixed optical power are shown for the focus shiftelements 14625 and the corrective lens element 14624, lenses withadjustable optical power can also be used, Adjustable lenses usingsliding lens elements (see U.S. Pat. No. 3,305,294) or liquid injectioncan be obtained for example from Adlens located in Oxford, UnitedKingdom: https://www.adlens.com/. Electrically adjustable lenses canalso be used as corrective lenses such as: liquid crystal lensesavailable from LensVector (Sunnyvale, Calif.) or liquid lenses availablefrom Varioptic (Lyon, France).

In addition, the optical modules can be mounted in the frame of thehead-worn display such that they are slightly pointed toward one another(also known as toe-in) to provide a convergence distance. Thus, theconvergence distance is established by the structural setup of theoptics in the head-worn display and vergence distance can be adjusted bylateral digital shifting of similar portions of the left and rightimages that are displayed to create disparity for a portion of an image.The convergence distance then establishes the baseline vergence distanceperceived by the user for stereo images that are rendered withoutdisparity. To provide an improved stereo viewing experience, theconvergence distance associated with the structural setup of the opticsmust be taken into account when rendering the disparity associated withdisplayed objects in stereo images. This is particularly important in ahead-worn display system wherein the focus distance and vergencedistance are matched for augmented reality objects in stereo images. Assuch the rendering of stereo images that were originally rendered forviewing in a theater, may need to be adjusted for improved viewing in ahead-mounted display. The convergence distance can also be used toestablish the perceived distance to the entire image if the stereo imageis rendered without disparity, this can be useful for applications suchas a head-worn computer wherein the desktop screen associated with thecomputer is perceived to be at a distance that is established by theconvergence distance. However, the convergence distance cannot be tooclose to the user since the left and right images will experienceopposing versions of keystone distortion. For example, a convergencedistance of 2.4 meters can be provided by pointing the optics modulestowards' each other by 0.75 degrees if the user's eyes are separated byapproximately 63.5 mm. The inventors have discovered that 0.75 degreesof toe-in results in a negligible level of keystone distortion. Closerconvergence distances require larger angles of toe-in and as such thekeystone distortion between the left and right images degrades theperceived sharpness in the corners of a stereo image. This keystonedistortion can be compensated for by rendering the left and right imageswith matching and opposite levels of keystone predistortion.

FIG. 147 shows an illustration of left and right optics modules that areconnected together in a chassis 14727 where the illustration is shownfrom behind the chassis 14727 where the user's eyes would be. Thechassis 14727 allows the optics modules to be built as a separate unitthat is assembled into a head-worn display. By making the chassis 14727structurally stiff, the optics modules can be physically alignedrelative to one another and the focus distance and convergence distancecan be checked and adjusted as necessary prior to being assembled intothe head-worn display thereby providing additional manufacturingflexibility.

FIG. 147 also shows the focus shift elements 14625 for the left andright optics modules connected in a focus shift element pair 14731. Byconnecting the focus shift elements 14625 together, it is easier to adda pair of focus shift elements when needed for augmented reality imagingat different distances. The connection between the focus shift elements14625 in a focus shift element pair 14731 can be rigid as shown in FIG.147 or flexible to enable the focus shift element pair 14731 to adjustto different spacing between the left and right optics modules withchassis' that have different widths for user's with different spacingbetween their eyes. Where focus shift elements 14625 with variousoptical powers are used to provide displayed images with different focusdistances for augmented reality activities that require the image to bedisplayed at different working distances. The focus shift elements 14625can also be different for the left and right eye to provide differentfocus distances for the left and right eyes. Focus shift elements 14625can also be provided without optical power so that they function as aprotective window for the upper optics 14510.

In the simplest form, a mode change associated with changing the focusdistance and vergence distance, can be accomplished by the userinputting information and selecting options through a user interfacesuch as buttons or a graphical user interface. Confirmation of the modechange can then be provided to the user on the displayed image such asfor example a colored box around the edge of the display field of viewor a message stating “Mode change initiated for arm's length display”.In a more automatic mode change, a sensor 14730 can be provided thatsenses the focus shift element pair 14731 so that the images can beautomatically presented with a lateral shift that provides a differentvergence distance that matches the focus distance provided by the focusshift elements 14625. The sensor 14730 can simply sense whether a focusshift element pair 14731 is present or not. Alternatively, the sensor14730 can detect a code (e.g. a barcode) on the focus shift element pair14731 that corresponds to the optical power or focus distance providedby the focus shift elements 14625 so that the displayed images can beautomatically digitally shifted laterally to provide a matching vergencedistance. The sensor can be located in the center as shown in FIG. 147,but other locations are also possible such as to one side. The code canbe on one of the optical surfaces or on the edge of the focus shiftelement 14625 and the sensor 14730 can be oriented in a correspondingfashion to read the code. If the focus shift elements 14625 are notconnected in a focus shift element pair 14731, then two sensors 14730can be provided with one sensor 14731 on each side. When a focus shiftelement 14625 is detected, the displayed image can be automaticallychanged in response to the change in operating mode that is implied bythe detected presence of a focus shift element 14625. In addition to thelateral shift to change the vergence distance as previously discussedherein, other changes can be made to the presentation of the displayedimage when a focus shift element is present including: the size, themagnification, the format (e.g. 4:3 instead of 16:9), the color, thecontrast, the dynamic range or the resolution. Where these changes tothe image, are done to improve the viewing experience for the user whenoperating at different display distances such as in augmented realityactivities. Changes in magnification and format are particularlyimportant with this mode change as the lateral shift of the image tochange the vergence distance results in some clipping of the availabledisplay field of view and the optical power associated with the focusshift element 14625 changes the overall optical power of the displayoptics.

FIGS. 148 and 149 show how displayed images can be digitally shiftedlaterally within the display field of view to change the vergencedistance seen by the user. FIG. 148 shows the left and right images,14841 and 14843 respectively, as provided at the nominal vergencedistance within the left and right display fields of view, 14840 and14842 respectively. Where the nominal vergence is established by thealignment of the optics modules relative to one another in the head-worndisplay. The nominal vergence distance can be for example, infinitywherein the optical axes of the left and right display fields of viewwould be parallel to each other. In a preferred embodiment, the opticalaxes of the left and right display fields of view (14840 and 14842) aretoed-in by approximately 0.75 degrees each, so that the nominal vergencedistance is established at approximately 2.4 meters for a typical userwith an interpupillary spacing between their eyes of 63.5 mm. FIG. 149shows how the left and right images 14941 and 14943 are shiftedlaterally towards each other within the left and right display fields ofview 14940 and 14942 respectively, to provide a shorter vergencedistance. By shifting the left and right images 14941 and 14943 towardseach other, the user's eyes must be pointed towards each other somewhatto view the left and right images 14941 and 14943 as a stereo pair witha shorter vergence distance. For improved comfort when viewing thestereo pair, the focus distance should be matched to the vergencedistance. In shifting the left and right images 14941 and 14943laterally, portions of the left and right display fields of view (shownas 14945 and 14946) become unusable for stereo imaging since those areasdo not overlap in the user's field of view. As such, the usable size ofthe left and right display fields of view 40 and 14942 is reduced whenthe head-worn display is used with a vergence distance other than thenominal vergence distance. The advantage of doing a digital shift of theleft and right images 14941 and 14943 to provide a different vergencedistance is that switching from the nominal vergence distance to adifferent vergence distance can be done without having to change thephysical setup of the optics modules in the head-worn display. To reducethe clipping of the display field of view, extra pixels can be used onthe image source that are not normally used to display images whenoperating in a mode where lateral shifting of the image is required. Forexample an image source with 1310×768 pixels can normally be used todisplay images that have 1280×720 pixels so that additional pixelsaround the edge are only used when the displayed image is digitallyshifted to change the vergence distance. Due to vignetting, thebrightness of the portion of the displayed image that is displayed withthe pixels around the edge may need to be increased.

As previously mentioned herein, changes in focus distance can also beprovided by changing the relative positioning of some of the elements inthe optics. FIGS. 150a and 150b show a mechanism for moving the imagesource 15044 relative to one or more lens elements 15012 in the upperoptics 14510 to provide a change in the focus distance of the displayedimage. Where typically moving the image source 15040 upward as shown inFIG. 150b moves the focus distance further away and vice versa. Themechanism shown includes an upper wedge 15042 and a lower wedge 15043along with solenoids 15035 and 15036 that respectively act on cores15037 and 15038. Where cores 15037 and 15038 are made of ferromagneticmaterials and are attached to the lower wedge 15043. Solenoids 15035 and15036 include cylindrical windings of conductive wiring so that when anelectrical current is applied to the wiring, the respective core 15037or 15038 is drawn into the solenoid and the attached lower wedge therebyis moved to one side or the other. the solenoids are fixed in positionrelative to the housing of the upper optics 14510. As the lower wedge15043 is moved laterally, the upper wedge 15042 is moved up and downalong with the image source 15040 which is attached to the upper wedge15042. Consequently, when a current is applied to the solenoid 15035,the lower wedge 15043 is moved to the left as shown in FIG. 150b , andas a result, the upper wedge 15042 is moved upward along with the imagesource 15040 and the focus distance is increased. Similarly, when acurrent is applied to the solenoid 15036, the lower wedge 15043 is movedto the right as shown in FIG. 150a , the upper wedge 15042 is moveddownward along with the image source 15040 and the focus distance isdecreased. By using upper and lower wedges 15042 and 15043 with arelatively shallow wedge angle (e.g. 5 to 15 degrees), the wedges tendto stay in place when the current to the solenoid is turned O150.Opposing permanent magnets (not shown) can be added to the wedges 15042and 15043 to increase the friction between the wedges and thereby assistin holding the wedges in place when the current to the solenoids isturned O150. In this way, the power required to operate the solenoids(15035 and 15036) can be very small even if a relatively large currentis required to generate enough force to move the lower wedge 15043. Byalternating the application of current to solenoids 15035 and 15036, thefocus distance can be alternately switched between two focus distancessuch between a 2.4 meter focus distance and a 0.6 meter focus distance.This method of changing the focus distance can be used with any opticsthat use a microdisplay at a focus plane of optics such as waveguidebased optics or beam splitter cube based optics. This arrangement mayalso be used with a pulsed application of current to the solenoids 15035and 15038 to cause a stepped change in wedge position and an associatedstepped change in focus distance that spans over a continuous range,multiple stepped range, etc. In addition, guidance to the movement ofthe image source 15040 can be provided by sliding pins that pass throughthe upper wedge 15042 or an associated structure (not shown), where thepins allow vertical movement and prevent lateral movement.

FIGS. 151a and 151b show illustrations of upper wedge 15042 and lowerwedge 15043 from the position of the image source 15040. As shown, thewedges 15042 and 15043 comprise rectangular structures with theircenters removed like a window frame so that illumination light and imagelight can pass through the wedges (15042 and 15043) to enable an imageto be displayed. This is important when the mechanism to move the imagesource 15040 is positioned below the image source 15040 (along theoptical path of the image light]. FIG. 151a corresponds to the wedgepositioning shown in FIG. 150a and FIG. 151b corresponds to the wedgepositioning shown in FIG. 150b . The advantage of the layout shown inFIGS. 150a and 150b is that the wedges 15042 and F43 and other pieces inthe mechanism do not increase the overall height of the upper optics14510.

In an alternate embodiment (not shown) the mechanism for moving theimage source 15040 is positioned above the image source 15040 and thenthe wedges (15042 and 15043) can be solid wedges or have portions of thecenter removed to enable wires to connect to the image source 15040. Theadvantage of positioning the wedges and other pieces of the mechanismabove the image source 15040 is that the image source can be positionedcloser to the lens elements 15012 which can be important in some opticaldesigns.

In another embodiment, the wedges (15042 and 15043) can be transparentand can cover the entire aperture of the image source 15040. Thetransparent wedges (f15042 and 15043) can operate as previouslydescribed to move the image source 15040. In addition, as the wedgesmove laterally, the combined optical thickness of the two wedges is afunction of the relative wedge position in the area that covers theactive area of the image source 15040. This is due to the fact that thetransparent wedges have a higher index of refraction than the air thatthey are replacing. Because the wedges are matched in slope, thecombined optical thickness of the area where the wedges are overlappedis uniform. As such, changes in the combined optical thickness of theoverlapped wedges contributes to changes in the focus distance.

To further improve the repeatability of the movement of the image source15040 and the upper wedge 15042 when the lower wedge 15043 moves, springclips can be used to apply a force to the image source 15040 or theupper wedge 15042 to insure contact is maintained between the surfaces.FIG. 152 shows an illustration of spring clips 15250 and 15252 applyinga force to an image source 15040 where the image source 15040 isattached to the upper wedge 15042. The spring clips 15250 and 15252 areattached to the housing of the upper optics 14510 using screws 15253,ultrasonic welding, adhesive or other connecting systems. To reducelateral movement of the image source 15040 as the lower wedge 15043 ismoved, one or both of the spring clips 15250 and 15252 can be connectedto the image source 15040 or the upper wedge 15042. In this way,vertical movement (as shown) is allowed for changing the focus distanceby flexing the spring clips 15250 and H52, while lateral movement is notallowed due to the higher stiffness of the spring clips in the lateraldirection particularly if both spring clips 15250 and 15252 areconnected to the image source 15040 or upper wedge 15042.

In another embodiment, the movement of the lower wedge 15043 iscontrolled by an electric motor and a lead screw instead of solenoids.Where the electric motor is connected to the housing of the opticsmodule and a lead screw or core is connected to the lower wedge 15043.The electric motor can be a conventional rotating motor, a linear motor,a vibrating piezoelectric motor, an induction motor, etc. The electricmotor can also be controlled to move the lower wedge 15043 differentdistances to provide various focus distances. The electric motor can bea stepper motor in which the number of steps determines the distance ofmovement. Sensors can also be provided to detect the movement of thelower wedge, lead screw or core to improve the accuracy of the movementand associated accuracy of the focus distance change.

In yet another embodiment, the movement of the lower wedge 15043 isprovided by a manually operated knob (not shown). The knob is connectedto a lead screw that is threaded into the lower wedge 15043. The userturns the knob to move the lower wedge and thereby affect a change inthe focus distance. This can be used for fine tuning of the sharpness ofthe displayed image as well for changing the focus distance to match agiven vergence distance or to match the focus distance to the distanceto a real object in the see-through view of the surrounding environment.

In a further embodiment, the corrective lens element 14624 can include amechanism (not shown) to enable the corrective lens element 14624 toslide upward or swing to the side, to thereby move out of the displayfield of view while still being attached to the head-worn display. Inthis way, the corrective lens element 14624 can be readily available foruse with the head-worn display. This can be useful as the correctiveacts simultaneously on both the displayed image and the see-through viewof the surrounding environment. There can be times when the user wouldwant to be able to change the focus distance of the displayed image orchange the focus of the see-through view of the surrounding environmentdepending on the activity that he is engaged in and having a readilyavailable corrective lens element 14624 would enable that. Inparticular, a corrective lens may be needed by the user when operatingat extreme focus distance such as arm's length or nearer, or atinfinity. In embodiments, the corrective lens 14624 may be manually orautomatically shifted into position.

In a yet further embodiment, eye cameras are included in the left andright optics modules to determine where the relative direction theuser's eyes are looking. This information can then be used to determinethe portion of the displayed image the user is looking at. The focusdistance can then be adjusted to match the vergence distance associatedwith augmented reality objects in that portion of the displayed image.The focus distance is then automatically adjusted as the user moves hiseye to different augmented reality objects or different portions ofaugmented reality objects within the displayed image. Alternatively theeye cameras can be used to determine the vergence of the user's eyes andthereby determine the distance that the user is looking at in thesee-through view of the surrounding environment. The focus distance orvergence distance can then be adjusted in correspondence to the distancethe user is looking at. Where the focus distance or vergence distancecan be automatically adjusted to either match the distance the user islooking at in the see-through view of the surrounding environment or tobe at a different distance so the displayed image doesn't interfere withthe user's view of the surrounding environment.

FIGS. 153a, 153b and 154 shows illustrations of example display opticsthat include eye imaging. FIGS. 153a and 153b show display optics thatinclude upper optics 14510 and a combiner 14520 to provide image light15370 to an eyebox 15366 where the user's eye would be positioned whenviewing a displayed image overlaid onto a see-through view of thesurrounding environment. An eye camera 15364 is provided on the side ofthe upper optics 14510 and angled towards the combiner 14520 to capturelight 15368 from the user's eye in the eyebox 15366 as reflected by thecombiner 14520. One or more LEDs 15362 are provided adjacent to theupper optics 14510 and pointed to provide illuminating light 15367 tothe eyebox 15366 and the user's eye either directly or as reflected froman optical surface such as the combiner 14520, when the head-worndisplay is being used by a user. Where the LED's 15362 can provideinfrared light 15367, provided the eye camera 15364 is sensitive toinfrared light.

FIG. 154 shows an illustration of display optics viewed from above, thatinclude projection optics 15410, a waveguide 15415 and holographicoptical elements 15417 and 15413. The projection optics 15410 caninclude one or more optical elements 15412 to modify the image light15470 as required to couple the image light 15470 into the holographicoptical element 15413 and into the waveguide 15415. The optical elements15412 can change the wavelengths of the image light 15470, change theformat of the image light 15470, change the size of the image light15470 or predistort the image light 15470 as needed to enable the imagelight 15470 to be presented to the user's eye 15466 in the desiredformat with reduced distortion. The optical elements 15412 can include:refractive lenses, diffractive lenses, toroidal lenses, freeform lenses,gratings or filters. Where the holographic optical element 15413deflects image light 15470 that has been provided by the projectionoptics 15410 into the waveguide 15415 where it is transported to theholographic optical element 15417. The holographic optical element 15417then deflects the image light 15470 toward the user's eye 15466 wherethe displayed image is viewed as an image overlaid onto a see-throughview of the surrounding environment. An eye camera 15464 is provided forcapturing images of the user's eye, as reflected by a surface of thewaveguide, when the head-worn display is being used by a user. One ormore LEDs 15462 are provided adjacent to the waveguide 15415 toilluminate the user's eye 15466 either directly or reflected from asurface of the waveguide and thereby increase the brightness of thecaptured images of the user's eye 15466. Where the LED's 15362 canprovide infrared light, provided the eye camera 15364 is sensitive toinfrared light.

To improve the efficiency of the eye imaging systems shown in FIGS.153a, 153b and 154, coatings can be applied to the surface that reflectslight from the eye toward the eye camera. The coating can be a hotmirror coating that reflects infrared light and transmits visible light.In this way, the eye camera can capture bright images of the user's eyewhile simultaneously providing the user with a bright see-through viewof the surrounding environment.

The eye camera (15364 or 15464) can include autofocus to automaticallyadjust a focus setting of the eye camera when the user's eye is in adifferent positions such as when the head-worn display is positioneddifferently on the user's head or when a different user is using thehead-worn display. Where the autofocus adjusts the relative position oflens elements or adjusts the optical power associated with adjustablelens elements in the optics associated with the eye camera to provide ahigher contrast in the images of the user's eye. In addition, theautofocus can automatically adjust focus when corrective lenses 14624are present and thereby compensate for the corrective lenses 14624. Inthis case, metadata saved with the images of the user's eye records therelative focus setting of the eye camera (15364 or 15464) and changes inthe metadata can be used to determine whether a corrective lens 14624 ispresent or not. If a corrective lens 14624 is present, adjustments tothe focus distance of the display optics can be made that take intoaccount the presence of the corrective lens 14624.

Images of the user's eyes can be used to determine the viewing directionthe user is looking by determining the relative position of the user'spupil within the eyebox or within the field of view of the eye camera15364. From this information the relative direction that the left andright eyes are looking can be determined. This relative directioninformation can be used to identify which portion of the displayed imagethe user is looking at. By comparing the relative direction of theuser's left and right eyes within simultaneously captured images, thedifference in relative direction between the left and right eyes and theinterpupillary distance between the user's eyescan be used to determinethe vergence viewing distance that the user is looking at. The vergenceviewing distance can be used to determine the focus distance andvergence distance needed in the displayed image to provide the user witha sharply focused augmented reality object in the displayed image. Thedetermined vergence viewing distance can also be compared to thevergence distance associated with the portion of the displayed imagethat the user is looking at, to determine whether the user is looking atthe displayed image or the see-through view of the surroundingenvironment. Adjustments can be made to the focus distance and vergencedistance for different portions of the displayed image to present theuser a sharply focused image in the portion of the image that the useris looking at or present the user with a blurry image in the portion ofthe image that the user is looking at as needed for the mode ofoperation or use case. Where digital blurring of portions of the imagecan be used to make portions of the image appear to have a focusdistance that is closer or farther away than the portions of the imagethat left with sharp imagery. In addition, the vergence viewing distancecan be compared with the disparity associated with the portion of astereo image that the user is looking at. The disparity of the stereoimage can then be adjusted locally at the portion of the image the useris looking at or scaled over the entire stereo image to present the userwith adjusted stereo depth over the entire image.

The head-worn display can include an inertial measurement unit todetermine the location, movement and gaze direction of the head-worndisplay. Where the inertial measurement unit can include: a locationdetermining system such as GPS, an electronic compass to determine gazedirection in the compass directions, accelerometers and gyroscopes todetermine movements and a tilt sensor to determine a vertical gazedirection. Comparing the viewing direction determined from the images ofthe user's eyes to the gaze direction determined by the inertialmeasurement unit can allow a compass heading to be determined for thedirection the user is looking. Combining the determined location withthe compass heading of the direction the user is looking can allowobjects in the surrounding environment to be identified that the user islooking at. This identification can be further improved by comparing thevergence viewing distance and the compass heading for the direction theuser is looking with objects in the surrounding environment known to bethat distance and direction from the user. This type of determinationcan be important for augmented reality and the display of augmentedreality objects relative to real objects.

To enable the focus distance to be adjusted as the user moves his eyesaround the field of view, the focus viewing distance must be determinedrapidly and a fast focus adjustment system is required. Vergence anddisparity within the stereo images must be adjusted in correspondence tothe determined changes in focus viewing distance. A response time of0.033 sec or less is typically required for imaging modifications withinhead-worn display systems to prevent the user's viewing experience frombeing adversely affected by latency such as the user experiencing nausea(see the paper “Tolerance of Temporal Delay in Virtual Environments” R.Allison, L. Harris, M. Jenkin, U, Jasiobedzka, J. Zacher, I149E VirtualReality 2001, 3/2001, p 247-254, ISBN 0-7695-0948-7). When a person'sgaze changes from a far object to a near object, the human eye canchange vergence viewing distance quickly while the focus adjusts moreslowly. To enable this, a fast frame rate (e.g. 60 frames/sec orgreater) is needed for capture of images of the user's eyes and theimages need to have high contrast to enable fast image analysis todetermine the relative positions of the user's eyes. The user's viewingdirection and the focus viewing distance can then be determined tofurther determine where and what the user is looking at. A fast focusdistance adjustment system is then needed to adjust the focus distancein 0.5 sec or less as the user moves his eyes.

FIGS. 153a, 153b , 154 show display optics that include a focus distanceadjustment module 15360 in the upper optics 14510 and projection optics15410 respectively. Where the focus distance adjustment modules 15360can provide fast mechanisms for moving the position of the image sourcerelative to the remaining lens elements thereby changing the focusdistance of the displayed image. It is important to realize that focusadjustment modules can be used in any type of display optics forhead-worn displays (e.g. wedge waveguides, waveguides with multiplereflective strips, holographic projection systems, (with the exceptionof laser scanning projection systems because they are not focused)because the movement of the image source relative to the other displayoptics to adjust the focus distance is fundamental to display optics andas such the focus adjustment modules are broadly useable in head-worndisplays.

FIGS. 155a, 155b, 156a, 156b, 157a, 157b, 158a, 158b, 159a and 159b showillustrations of focus adjustment modules 15360 with mechanisms that canprovide fast focus distance adjustment. To be effective for fast focusdistance adjustment in a head-worn display, the focus adjustment modules15360 need to be fast, quiet, provide approximately 0.5 mm travel,compact, provide guidance to maintain alignment between the image source15040 and the remaining optics without tilt, controllable over the focusdistance range, low cost and low weight.

In a preferred embodiment, to provide a change in focus distance withoutchanging the size of the displayed image, display optics are providedthat are telecentric at the image source. Where telecentric displayoptics provide parallel light ray bundles so that the area of the imagesource that is imaged by the display optics remains constant regardlessof changes in the distance between the image source and the remainingoptics as required to change the focus distance for the displayed image.In certain embodiments the image source is reflective and theillumination light provided by the illumination source may betelecentric as well. Where, telecentric illumination light can beprovided by an illumination source that is at least the same size as theimage source and provides a wider cone of light where only thetelecentric portion of the cone is reflected by the image source. Thus,telecentric display optics at the image source provide an improvedviewing experience for augmented reality, particularly when rapidchanges to focus distance are being provided as the user moves theireyes around the field of view. Under this use case scenario, usingnon-telecentric display optics at the image source would result indisplayed augmented reality objects that changed slightly in size eachtime the user moved their eyes and nausea would likely result. Incontrast, by using telecentric display optics, focus distance can becomfortably changed continuously as the user moves their eyes around thefield of view. FIG. 161 provides an illustration of an example ofnon-telecentric display optics where the rays bundles of the image light16150 are converging as the image light 16150 proceeds from the imagesource 15040 toward the display optics including the powered prism16140. As a result, if the image source 15040 is moved closer to thepowered prism 16140, the lens 16145 and combiner 16150 in the displayoptics, the image appears to get smaller when viewed by the user fromthe position of the eyebox 16155 and vice versa. In contrast, FIG. 162shows an illustration of example telecentric optics including forexample powered prism 16240 and lens 16245 wherein the ray bundles ofthe image light 16250 are parallel to each other. Consequently as theimage source 15040 is moved closer or farther from the powered prism16140, the image remains the same size in the displayed image as viewedby the user from the eyebox 16155.

FIGS. 155a, 155b, 156a, 156b, 157a, 157b, 158a and 158b show actuatorsand guidance mechanisms positioned between the image source and theremaining optics. Each of the figured 155, 156, 157, and 158 illustratedifferent mechanisms in two states. In contrast, FIGS. 159a and 159bshow actuators and guide mechanisms positioned between the image source15040 and the top of the housing for the focus adjustment module 15360.Any of the actuators and guidance mechanisms shown can be used in eitherposition with some modifications (not shown). The choice of where toposition the actuators and guidance mechanisms depends on where space isavailable in the display optics and the housing for the head-worndisplay. If the space for the actuators and guidance mechanisms islimited in the display optics, the actuators and guidance mechanisms arepositioned above the image source as shown in FIGS. 159a and 159b .However, by positioning the actuators and guidance mechanisms above theimage source, the height of the display optics can be substantiallyincreased. Therefore in a preferred embodiment, multiply folded (alsoknown as compound folded] display optics are included so the actuatorsand guidance mechanisms can be positioned adjacent to the image source,and as a result, the height of the display optics is reduced. FIG. 160shows an illustration of an example of multiply folded optics as viewedfrom the eye position, wherein the optical axis is folded to the side inthe upper optics 16010 to reduce the height of the upper optics 16010.The image source 15040 is then positioned to the side of the upperoptics 16010 and the image source 15040 is approximately verticalinstead of horizontal. Where in the example folded optics shown in FIG.160 are included, one or more lenses 16012, a fold mirror 16013 thatredirects image light 15370 from the upper optics 16010 toward acombiner 14520, that redirects the image light toward the eyebox 15366and the user eye. In the folded optics shown in FIG. 160, the foldmirror 16013 is a reflective polarizer so that a backlight 16014 can bepositioned behind the fold mirror 16013 to provide P polarizedillumination light 16071 that illuminates a reflective image source inthe focus adjustment module 15360 such as an LCOS. In reflecting theillumination light 16071, the image source 15040 changes thepolarization state from P to S, thereby providing S polarized imagelight 15370, which is reflected by the fold mirror 16013. By usingmultiply folded optics, the focus adjustment module 15360 includingactuators and guidance mechanisms can be positioned to one side of theupper optics 16010 where more space can be available in the frame of thehead-worn display. Alternatively, the fold mirror can be included in aprism as shown in FIGS. 161 and 162, that can also include surfaces withoptical power to further reduce the size of the display optics. As aresult, multiply folded display optics provide the advantage of enablinga more compact head-worn display when the display optics include focusadjustment modules 15360.

FIGS. 155a and 155b show an illustration of a focus adjustment modulethat includes a set of wedges 15042 and 15043 as actuators, wherein thelower wedge 15043 moves laterally to move the image source 15040vertically (as shown) to change the position of the image source 15040relative to the remaining optics comprising lens elements 15012 or lenselements 15412. Solenoids 15035 and 15036 are provided to act onferromagnetic cores 15037 and 15038 respectively, where the cores 15037and 15038 are attached to the lower wedge 15043. Because the wedges15042 and 15043 are positioned between the image source 15040 and theremaining optics of display optics, the wedges 15042 and 15043 are madewith a center window as shown in FIGS. 151a and 151b so that light canpass from the remaining optics to the image source 15040. Applying anelectrical current to solenoid 15035 will attract core 15037 and causethe lower wedge 15043 to move to the left, thereby causing the upperwedge 15042 and the attached image source 15040 to move downward whichdecreases the focus distance as shown in FIG. 155a . Similarly, applyingan electrical current to solenoid 15036 will attract core 15038 andcause the lower wedge 15043 to move to the right, thereby causing theupper wedge 15042 and the attached image source 15040 to move upwardswhich increases the focus distance as shown in FIG. 155b . A leaf spring15570 has been provided to apply a force against the upper wedge 15042or image source 15040 so that the wedges are help in alignment duringthe movement of the wedges. The leaf spring can also be attached to thehousing of the focus adjustment module 15360 and to the image source15040 or the upper wedge 15042 to prevent lateral movement of the imagesource during movement of the wedges, thereby providing guidance to theimage source during focus adjustments.

FIGS. 156a and 156b show illustrations of a focus adjustment module15360 that includes a pair of bimorph piezoelectric actuators 15675 andM76 to move the image source 15040 for focus adjustments. Where abimorph piezoelectric actuator is comprised of two laminated strips ofpiezoelectric material arranged so that when a voltage is applied to thetwo strips, one side of the bimorph contracts while the other side ofthe bimorph expands, thereby causing the actuator to go from flat tocurved. Bimorph piezoelectric actuators are advantageous for use in afocus adjustment module 15360 because they are fast acting, compact andthey can provide much more displacement than piezoelectric stackactuators. With the bimorph piezoelectric actuators 15675 and 15676shown in FIGS. 156a and 156b , one end is attached to the housing of thefocus adjustment module 15360 and the other end pushes on a carrier15677 that is attached to the image source 15040. FIG. 156a shows a flatstate for the bimorph piezoelectric actuators 15675 and 15676, whileFIG. 156b shows a curved state for the bimorph piezoelectric actuators15675 and 15676. Where the carrier 15677 supports the image source 15040around the edge and the center portion of the carrier is removed to forma window so that light including illumination light and image light, canpass from the image source 15040 to the remaining optics as previouslydescribed herein for wedges 15042 and 15043. When a voltage is appliedto the two bimorph piezoelectric actuators 15675 and 15676, both of theactuators 15675 and 15676 curl upwards thereby causing the carrier 15677and attached image source 15040 to move upwards as shown in FIG. 156band the focus distance then increases. If more voltage is applied thebimorph piezoelectric actuators 15675 and 15676 will curl more. When thevoltage is removed, the bimorph piezoelectric actuators 15675 and 15676to return to a flat state, as shown in FIG. 156a and the focus distancedecreases. The actuators are shown arranged to lift opposite corners ofthe carrier to provide a vertical lifting force. If a faster response isdesired in the movement from the curved state shown in FIG. 156b to theflat state shown in FIG. 156a , the voltage applied to the bimorphpiezoelectric actuators can be reversed in sign for a short period oftime. However, if the reversed voltage is applied for a long enough timefor the actuators 15675 and 15676 to reach steady state, the actuatorswill curve in the reverse direction which will cause the carrier 15677and the attached image source 15040 to be lifted somewhat. In addition,as shown in FIGS. 156a and 156b , a four bar linkage 15679 has beenprovided. Wherein the four bar linkage 15679 is attached to the sidewallof the housing of the focus adjustment module 15360 and to four pointson the carrier 15677. The function of the four bar linkage 15679 is toprovide guidance of the carrier 15677 and attached image source 15040 sothat the image source 15040 doesn't move laterally or tilt relative tothe remaining optics so that alignment is maintained during movementsassociated with focus adjustments. The four bar linkage 15679 shown inFIGS. 156a and 156b is a thin metal or plastic structure with flexiblefingers that extend from the sidewall attachment to the attachmentpoints on the carrier 15679. The flexibility of the fingers allows forunimpeded vertical movement while preventing lateral movement. Thecarrier 15677 is designed to provide attachment points that are spacedapart vertically as shown thereby enabling the fingers of the four barlinkage 15679 to prevent tilt of the carrier and attached image sourceduring vertical movement. The four bar linkage 15679 can be furtherdesigned to be a leaf spring so that a slight downward force is appliedto the carrier 15677 to ensure that the carrier 15677 remains in contactwith the bimorph piezoelectric actuators 15675 and 15676 during focusadjustments. The advantage of this arrangement of the bimorphpiezoelectric actuators is that a large displacement can be provided fora larger focus adjustment. In embodiments, the linkage 15679 may have astop at an upper position to more accurately stop the translation of thecarrier 15677 in an upper position. In embodiments, a stop may beotherwise positioned to create an upper boundary for the carrier. Infurther embodiments, the voltage applied to the bimorph piezoelectricactuators can be reversed to cause the bimorph piezoelectric actuatorsto bend in the opposite direction (not shown) and thereby extend theuseable displacement range for focus adjustment.

FIGS. 157a and 157b show illustrations of another version of a focusadjustment module 15360 that includes bimorph piezoelectric actuators15781 and 15782. In this case, the lower bimorph piezoelectric actuator15781 is attached in the middle to the lower surface of the housing ofthe focus adjustment module 15360 and the upper bimorph piezoelectricactuator 15782 is attached in the middle to the lower surface of thecarrier 15677. The ends of the upper bimorph piezoelectric actuator15782 and the lower bimorph piezoelectric actuator 15781 are attachedtogether. FIG. 157a shows the flat state wherein no voltage is appliedto the bimorph piezoelectric actuators 15781 and 15782. When a voltageis applied to the bimorph piezoelectric actuators 15781 and 15782, theyboth change to a curved state, which causes the carrier 15677 and theimage source to move vertically thereby increasing the focus distance.As more voltage is applied, the curve of the actuators 15781 and 15782becomes more pronounced and the movement of the carrier 15677 and thechange in focus distance is increased. The advantage this arrangement ofthe bimorph piezoelectric actuators 15781 and 15782 is that a largerlifting force and faster movement can be provided, but the displacementis less. Consequently, the bimorph piezoelectric actuators 15781 and15782 are arranged back-to-back so they curl in opposite directions whena voltage is applied thereby doubling the displacement of the carrierfor a given voltage. The use of more than two bimorph piezoelectricactuators (e.g. four bimorph piezoelectric actuators) in a stack ispossible. As previously described herein, a four bar linkage is provideto guide the movement of the carrier 15677 and attached image source15040 to prevent lateral movement or tilt during focus adjustments.

FIGS. 158a and 158b show illustrations of a focus adjustment module15360 that includes one or more scissors jack actuator actuators 15883.Where the scissors jack actuator includes a frame that flexes so thatthe upper point moves further upward as a center shaft 15885 shortens.In this way, the frame of the scissors jack actuator 15883 acts as adisplacement amplifier so that the movement of the carrier 15677 isgreater than the change in length of the center shaft 15885. FIG. 158ashows the state when the center shaft 15885 is long, thereby causing theupper point to be lower and the carrier 15677 that sits on the scissorsjack actuator 15883 to be lower and as a result the focus distance isnearer to the user. FIG. 158b shows the state when the center shaft15885 is short, thereby causing the upper point to be higher and thecarrier 15677 that sits on the scissors jack actuator 15883 to also behigher and as a result the focus distance is farther from the user. Thecenter shaft 15885 can be a variety of devices that effectively changethe distance between the ends of the scissors jack actuator 15883 forexample, the center shaft 15885 can be a piezoelectric stack actuatorthat is actuated with an applied voltage or a screw that is actuatedmanually by turning by hand or actuated electrically by an electricmotor. In any case, the scissors jack actuator 15883 pushes on thecarrier 15677 to lift the image source 15040 thereby increasing thefocus distance. As previously described herein, a four bar linkage 15679can be provided to guide the carrier during focus adjustments topreserve the alignment of the image source 15040 relative to theremaining optics in the upper optics 14510. Piezoelectric stackactuators can provide very fast and precise movements so that if apiezoelectric stack is used as the center shaft 15885, very fast andprecise focus adjustments can be provided by a focus adjustment module15364 if it includes a piezoelectric stack actuator with a scissors jackactuator 15883.

FIGS. 159a and 159b show illustrations of focus adjustment modules 15360with voice coil motor actuators 15987. As previously described herein,in this case the image source 15044 is shown positioned below theactuator and the guidance mechanisms. A carrier 15977 is attached to theimage source 15040 to support the image source 15040 and provideattachment points for the four bar linkage 15679. Where the four barlinkage 15679 provides guidance to the carrier 15977 and attached imagesource 15040 during movement associated with focus adjustments. Theouter portion of the voice coil motor 15987 is attached to the uppersurface (as shown) of the housing of the focus adjustment module 15360and the inner portion is attached to the carrier 15977. FIG. 159a showsthe relative positions of the components when no voltage is applied tothe voice coil motor 15987. As shown, in FIG. 159a , the inner portionof the voice coil motor 15987 is extended so that the carrier is in alower position thereby providing a decreased focus distance. FIG. 159bshows the relative positions of the components when a voltage is appliedto the voice coil motor 15987. Under these conditions as shown in FIG.159b , the inner portion of the voice coil motor 15987 is retracted sothat the carrier is in a raised position thereby providing an increasedfocus distance. As more voltage is applied to the voice coil motor15987, the inner portion of the voice coil motor 15987 is retractedfurther thereby providing a greater change in focus distance. A spring(not shown) can be included in the focus adjustment module 15360 toapply a force to the carrier to decrease the time for the carrier tomove back to the position shown in FIG. 159a when the voltage is removedfrom the voice coil motor 15987. The spring can also assist in holdingthe carrier 15977 in the position shown in FIG. 159a to provide adefault focus setting when no power is applied to the voice coil motor15987 to thereby provide a low power operating mode.

A position measurement device (not shown) can be added to any of thefocus adjustment modules 15360 shown in FIGS. 155a, 155b, 156a, 156b,157a, 157b, 158a, 158b, 159a and 159b to measure the relative positionof the image source. The position measurement device can then provide ameasurement that can be used in a control system for focus distance thatcan be a closed loop control system to improve the accuracy andrepeatability of focus distance adjustments.

In a yet further embodiment, the position of the image sources 15040 inthe left and right optics modules can be adjusted in alignment step toprovide a reliable convergence distance. Where the alignment stepincludes positioning the chassis C27 in a jig that is aligned with atarget located in front of the jig and at the desired convergencedistance. A matched image is then displayed on the image source 15040and the image source 15040 is moved to align the displayed to the targetas viewed through the optics module. The advantage of adjusting theposition of the image source 15040 in an alignment step is that theeffects of variations in the dimensions of the chassis 14727, upperoptics 14510 and combiner 14520 can be compensated for to provide areliable convergence distance in a manufacturing environment.

In another embodiment, one or more of the following elements can beconnected to provide a removable assembly, including: the focus shiftelement, the combiner and the corrective lens element. This can providea more easily replaceable assembly which can be changed when damageoccurs, when the use case changes or the user changes. In particular, itis useful to change the focus shift element and the corrective lenselement at the same time when changing from a use case where thevergence viewing distance changes from a longer distance to a shorterdistance and vice versa. As in this use case, one or the other of thevergence viewing distances may be beyond what the user's eyes cancomfortable focus at. For example, if the user is near sighted then acorrective is needed when the vergence viewing distance is longer andnot needed when the vergence viewing distance is shorter.

The inventors have discovered that when world-locked digital contentshifts out of the field of view of a user's head-worn see-throughcomputer display it can create a less than optimal experience. When theuser's turns his head away from the point in the world where the digitalcontent is locked, for instance, the digital content shifts towards theside of the field of view. As the user turns his head even further, thecontent shifts out of the field of view and abruptly cuts off at theedge of the field of view. The abruptness of the change in appearanceand the ultimate complete loss of the content once the head turns farenough does not create a natural impression of the content being fixedin the real world. Normally, when viewing an actual object in ourenvironment, the object stays visually present, even if slightlypresent, until we shift our vision completely away from the object. Anobject that is shifted to the side of our direct line of sight visionmay be slightly blurry do to the nature of our vision (i.e. foviatedvision), but it remains present to some extent. In a typical see-throughhead-worn display the field of view has a limited area (e.g. width andheight). Typically, one can see through to the environment outside ofthe field of view so it seems odd when the content begins and ultimatelydisappears from the user's vision when the user can still see into theenvironment where the content was once present and locked.

An aspect of the present invention relates to generating a smoothtransition of world-locked augmented reality content that is shiftingout of a see-through field of view. In embodiments, the world-lockedcontent is modified to appear less apparent to the user as the contentshifts towards the edge of the field of view. This may take the form ofde-focusing, blurring, reducing the resolution, reducing the brightness,reducing the sharpness, reducing the contrast, etc. of the content as itis shifted towards the edge. The content may decrease in appearancegradually as it approaches the edge such that as it shifts past the edgeit's appearance is minimal or non-existent such that it appears to havegradually disappears from the user's sight. This may work particularlywell in a system that has a field of view that is large enough toaccommodate sharp content in the middle of the field of view but largeenough such that the user does not use the edges very much. For example,in a system with a horizontal field of view of 60 degrees, the outer 10degrees on both sides may be used as a transitional area whereworld-locked content is managed to reduce its appearance in preparationfor its disappearance from the field of view.

In one embodiment of a system for generating a smooth transition ofworld-locked augmented reality content that is shifting out of asee-through field of view, a head-worn see-through display that includesa see-through optical element mounted such that it is positioned infront of a user's eye when the head-worn see-through display is worn bythe user also includes a processor that is adapted to present digitalcontent in a field of view on the see-through optical element. Thedigital content may have a position within the field of view that isdependent upon a position in the surrounding environment. The processormay be further adapted to modify an appearance of the content as thecontent approaches an edge of the field of view such that the contentappears to disappear as the content approaches the edge of the field ofview. The appearance modification may be a change in the content'sbrightness, a change in the content's contrast, a change in thecontent's sharpness, or a change in the content's resolution. Theprocessor may include a display driver or an application processor. Theprocessor may be further adapted to generate a secondary field of view(e.g. through an additional optical system as described herein) in whichthe user views presented digital content and through which the user seesthe surrounding environment, the processor further adapted to transitionthe content from the field of view to the secondary field of view. Inthis further adaptation, the appearance of the content in the secondaryfield of view may be diminished as compared to the appearance of thecontent in the field of view. In this further adaptation, the secondaryfield of view may have a lower resolution than a resolution of the fieldof view, and may be generated by one of reflecting image light onto acombiner that directs the image light directly to an eye of the user ortowards a culminating partial mirror that reflects the image light to aneye of the user, an OLED that projects light onto a combiner, an LEDarray that projects light onto a combiner, or an edge lit LCD thatprojects light onto a combiner. In this further adaptation, thesecondary field of view may be presented by a see-through panelpositioned directly in front of an eye of the user, wherein thesee-through panel is mounted on a combiner and/or vertically. Thesee-through panel may be an OLED or an edge lit LCD. The processor maybe further adapted to predict when the content is going to approach theedge of the field of view and to base the appearance transition at leastin part on the prediction. The prediction may be based at least in parton an eye-image.

In embodiments, the prediction that the content is going to approachand/or go past the edge of the field of view may be determined based ona compass in the head-worn computer (e.g. monitoring the compass headingas compared to the world-locked position for the content), movement ofthe content within the field of view (e.g. monitoring where the contentis within the field of view and monitoring a direction and speed of itsmovement towards an edge), eye position (e.g. monitoring eye positionand movement as an indication of how the head-worn computer may move.There are times when the eyes shift prior to the head turning and theeye shift may provide the indication that the content appearance shouldbe managed), and/or a combination of these techniques.

In one embodiment of a system for prediction based transition ofworld-locked content, a head-worn see-through display may include asee-through optical element mounted such that it is positioned in frontof a user's eye when the head-worn see-through display is worn by theuser and a processor adapted to present digital content in a field ofview on the see-through optical element, wherein the digital content hasa position within the field of view that is dependent upon a position inthe surrounding environment. The processor may be further adapted topredict when the digital content is going to shift out of the field ofview due to a positional change of the head-worn see-through display andto modify the appearance of the content as the content approaches anedge of the field of view such that the content appears to disappear asthe content approaches the edge of the field of view. The prediction maybe based on a compass heading indicative of a forward facing directionof the head-worn see-through display or a tracked eye movement of theuser, wherein the tracked eye movement is indicative that the user isgoing to turn the user's head. The appearance modification may be achange in the content's brightness, a change in the content's contrast,a change in the content's sharpness, or a change in the content'sresolution. The processor may include a display driver or an applicationprocessor. The processor may be further adapted to generate a secondaryfield of view in which the user views presented digital content andthrough which the user sees the surrounding environment, the processorfurther adapted to transition the content from the field of view to thesecondary field of view. In this further adaptation, the appearance ofthe content in the secondary field of view may be diminished as comparedto the appearance of the content in the field of view. In this furtheradaptation, the secondary field of view may have a lower resolution thana resolution of the field of view, and may be generated by one ofreflecting image light onto a combiner that directs the image lightdirectly to an eye of the user or towards a culminating partial mirrorthat reflects the image light to an eye of the user, an OLED thatprojects light onto a combiner, an LED array that projects light onto acombiner, or an edge lit LCD that projects light onto a combiner. Inthis further adaptation, the secondary field of view may be presented bya see-through panel positioned directly in front of an eye of the user,wherein the see-through panel is mounted on a combiner and/orvertically. The see-through panel may be an OLED or an edge lit LCD. Theprocessor may be further adapted to predict when the content is going toapproach the edge of the field of view and to base the appearancetransition at least in part on the prediction. The prediction may bebased at least in part on an eye-image.

FIG. 163A illustrates an abrupt change in appearance of content 16302 inthe field of view of a see-through display. FIG. 163B illustrates amanaged appearance system where the content is reduced in appearance asit enters a transitional zone 16304 near the edge of the field of view.

An aspect of the present invention relates to a hybrid see-throughdisplay system where a high quality display system presents content to afield of view that is centered on the user's straight forward line ofsight and another lower quality system is used to present contentoutside of the straight forward line of sight. The content appearancetransition may then be managed in part in the center field of view andin the extended field of view. The extended field of view may have morethan one section as well, such that imagery may be presented in a nearedge portion and lighting effects are presented further out.

To illustrate, a front lit reflective display, emissive display,holographic display (e.g. as described herein) may be used to presenthigh quality content in a 40 degree field of view and another displaysystem may be used to present content or visually perceptive effectsfrom the edge of the 40 degree point (or overlapping or with a gap) outto some other point (e.g. 70 degrees). In embodiments, the outer fieldof view coverage (generally referred to as the “outer display”) mayoperate through an optical system in an upper module, proximate the mainfield of view display system, and the optical path may include folds(e.g. as generally described herein). In other embodiments, the outerdisplay may be a direct system where, for example, the image light oreffects light is generated and directed to the combiner. For example, adisplay may be mounted above the combiner and arranged to directlighting effects directly to the combiner.

In embodiments, the outer display may be included within the maindisplay. For example, the lensing system in the upper module may beadapted to generate high quality content in the middle but then lowerquality toward the edges of a larger field of view. In this system,there may be only one display (e.g. LCoS, OLED, DLP, etc.) and thecontent towards the edge of the display may be managed to effect theappearance transition.

FIG. 164 illustrates a hybrid field of view that includes a centeredfield of view 16402 for the presentation of sharp and transitionalcontent and an extended field of view 16404 that is positioned at ornear or overlapping with an edge of the centered field of view 16402 andadapted to provide lower appearance content and/or lighting effects thatassist in the transition of the world locked content as it shifts out ofthe center field of view 16402.

FIG. 165 illustrates a hybrid display system where the main, centered,field of view is generated with optics in an upper module 16502 (e.g. asdescribed herein elsewhere) and the extended field of view is generatedwith a display system mounted 16504 above the combiner and providingimage content and/or lighting effects in the extended area. Inembodiments, the extended field of view display 16504 may include anOLED, edge lit LCD, LED, or other display and the display may includemicro-lenses, macro-lens, or other optics to properly align and focusthe light. In embodiments, the extended field of view may include asingle lighting element, such as an LED, line or elements, array ofelements, etc.

In yet other embodiments, the extended field of view area may be createdby mounting a see through display on the combiner. For example, asee-through OLED display, edge lit LCD, etc. may be mounted in theextended field of view area and controlled to produce the transitionalimages and/or lighting effects.

In embodiments, a head-worn see-through display may be adapted totransition content to an extended FOV with reduced display resolution.The head-worn see-through display may include a see-through opticalelement mounted such that it is positioned in front of a user's eye whenthe head-worn see-through display is worn by the user and a processoradapted to present digital content in a main field of view on thesee-through optical element in which a user views presented digitalcontent and through which the user sees a surrounding environment, theprocessor further adapted to present digital content in an extendedfield of view in which the user views presented digital content andthrough which the user sees the surrounding environment. The main fieldof view may have a higher resolution than the extended field of view;and the processor further adapted to present a world-locked positioneddigital content in the main field of view and transition thepresentation of the world-locked positioned digital content to theextended field of view as the head-worn display changes position causingthe world-locked positioned digital content to transition out of themain field of view. The processor may include display driver or anapplication processor. The extended field of view has a resolution thatgenerates a substantial blur to content as compared with the content aspresented in the main field of view. The extended field of view may begenerated by reflecting image light onto a combiner that directs theimage light directly to an eye of the user, by reflecting image lightonto a combiner that directs the image light towards a culminatingpartial mirror that reflects the image light to an eye of the user, byan OLED that projects light onto a combiner, by an LED array thatprojects light onto a combiner, by an edge lit LCD that projects lightonto a combiner, or by a see-through panel positioned directly in frontof the eye of the user. The panel may be mounted on a combiner orvertically and may be an OLED or edge lit LCD. The processor may befurther adapted to predict when the content is going to approach theedge of the field of view and to base the appearance transition at leastin part on the prediction. The prediction may be at least in part basedon an eye-image.

FIGS. 166A-166D illustrate examples of extended display, or extendedimage content optic, configurations. As illustrated, the extendeddisplay configuration may be adapted to produce extended content and/orlighting effects around each side of the center display, on multiplesides of the center display or on one side of the center display.

FIG. 167 illustrates another optical system that uses a hybrid opticalsystem that includes a main display optical system 16502 and an extendedfield of view optical system 16504. In this embodiment, both opticalsystems project image light, extended image light, and/or lightingeffects to a combiner that reflects the light to a forward culminatingpartial mirror, which in turn reflects the light towards the wearer'seye.

In yet further embodiments, the extended field of view display may beprovided by a see-through display positioned in front of the user's eyesuch that the user looks directly through the see-through display. Forexample, a see-through OLED display or edge lit transparent LCD displaymay be positioned on either side of the combiner as illustrated infigures C and E or on either side of a waveguide or other display system(e.g. as illustrated in FIGS. 8a, 8b, 8c, 141a, 141b, 142a, 142b , 143,and 144).

In embodiments, a head-worn see-through display may be adapted toprovide an extended FOV for large content. The head-worn see-throughdisplay may include a see-through optical element mounted such that itis positioned in front of a user's eye when the head-worn see-throughdisplay is worn by the user, and a processor adapted to present digitalcontent in a main field of view on the see-through optical element inwhich a user views presented digital content and through which the usersees a surrounding environment, the processor adapted to present digitalcontent in an extended field of view in which the user views presenteddigital content and through which the user sees the surroundingenvironment. The main field of view may have a higher resolution thanthe extended field of view. The processor may be further adapted topresent a first portion of the digital content in the main field of viewand a second portion of the digital content in the extended field ofview. For example, when the digital content is too large to fit in themain field of view, the processor may create a soft transition betweenthe first portion of the digital content in the main field of view andthe second portion of the digital content in the extended field of viewsuch that it does not appear to be abruptly cut off at the edge of themain field of view. The processor may be adapted to generate a softappearance towards the edges of the main field of view. The processormay modify how pixels towards an edge of the display render content. Thehead-worn display of may further include a display driver that modifieshow pixels towards an edge of the head-worn display render content. Thehead-worn display may have pixels towards an edge of the head-worndisplay that render content differently than pixels towards a centerportion of the head-worn display. The pixels towards the edge may haveless gain than the pixels towards the center portion of the head-worndisplay. The pixels towards the edges of the main field of view may bealtered digitally through a content transition algorithm. The extendedfield of view may be generated by reflecting image light onto a combinerthat directs the image light directly to an eye of the user, byreflecting image light onto a combiner that directs the image lighttowards a culminating partial mirror that reflects the image light to aneye of the user, by an OLED that projects light onto a combiner, by anLED array that projects light onto a combiner, by an edge lit LCD thatprojects light onto a combiner, or by a see-through panel positioneddirectly in front of the eye of the user. The panel may be mounted on acombiner or vertically. The see-through panel may be an OLED or an edgelit LCD. The processor may be further adapted to predict when thecontent is going to approach an edge of the field of view and to basethe appearance transition at least in part on the prediction. Theprediction may be at least in part based on an eye-image.

In embodiments, a head-worn see-through display may be adapted to adjustcontent for transition to an extended FOV. The head-worn see-throughdisplay may include a see-through optical element mounted such that itis positioned in front of a user's eye when the head-worn see-throughdisplay is worn by the user and a processor adapted to present digitalcontent in a main field of view in which a user views presented digitalcontent and through which the user sees a surrounding environment. Theprocessor may be further adapted to present digital content in anextended field of view in which a user views presented digital contentand through which the user sees the surrounding environment. The mainfield of view may have a higher resolution than the extended field ofview. The processor may be further adapted to present digital content inthe main field of view and reduce an appearance of the content as thecontent approaches an edge of the main field of view. The processor mayyet be further adapted to further reduce the appearance of the contentwhen the content is presented in the extended field of view. Theprocessor may gradually reduce the appearance of the content in theextended field of view the closer the content gets to an edge of theextended field of view. The content may be substantially not apparentwhen the content is at the edge of the extended field of view. Theappearance reduction may be a reduction in the content's brightness, areduction in the content's contrast, a reduction in the content'ssharpness, or a reduction in the content's resolution. The extendedfield of view may be generated by reflecting image light onto a combinerthat directs the image light directly to an eye of the user, byreflecting image light onto a combiner that directs the image lighttowards a culminating partial mirror that reflects the image light toall eye of the user, by an OLED that projects light onto a combiner, byan LED array that projects light onto a combiner, by an edge lit LCDthat projects light onto a combiner, or by a see-through panelpositioned directly in front of the eye of the user. The panel may bemounted on a combiner or vertically. The see-through panel may be anOLED or an edge lit LCD. The processor may be further adapted to predictwhen the content is going to approach an edge of the field of view andto base the appearance transition at least in part on the prediction.The prediction may be at least in part based on an eye-image.

FIGS. 168A-168E illustrate various embodiments where a see-throughdisplay panel 16802 (e.g. OLED, edge lit transparent LCD display) ispositioned directly in in front of the user's eye in the head-worncomputer to provide the extended and/or overlapping field of view in ahybrid display system. FIG. 168A illustrates a system where the extendedfield of view is provided by the transparent display panel 16802 mountedon or near the combiner optic. In this embodiment, the see-throughdisplay panel 16802 is mounted on or near the back of the combiner suchthat it does not interfere with the center display system that reflectsimage light off the combiner directly to the user's eye. FIG. 168Billustrates a hybrid display system where the see-through extended fieldof view display panel 16802 is positioned vertically proximate thecombiner. FIG. 168C illustrates a hybrid display system where thesee-through extended field of view display panel 16802 is mountedvertically in front of a curved partial mirror of the main field of viewdisplay.

FIGS. 168D and 168E illustrate hybrid display systems from the rear(i.e. user's view]. FIG. 168D illustrates a system where the see-throughextended field of view display panel 16802 surrounds the main field ofview see-through display. FIG. 168E illustrates a system where theextended field of view see-through display panel 16802 is on the sidesof the main field of view display system. It should be understood thatthe inventors envision that the extended field of view display panel maybe configured in a number of different ways to provide the extension onone or more sides of the main field of view and in a balanced (i.e.similar extension on more than one side) or unbalanced (i.e. more orless extension on one or more sides) configuration. It should also beunderstood that the inventors envision that the extended field of viewmay overlap the main field of view, appear adjacent to the main field ofview, have a gap between the main field of view and the extended fieldof view, etc., depending on the specific needs of the situation.

While the configurations described herein with respect to the extendedfield of view have been illustrative of creating a system where smoothtransitioning of world-locked content, these configurations may furtherbe used to create additional lighting effects and or shadowing effectsfor content displayed in the main field of view. For example, in aconfiguration where the extended field of view see-through displayoverlaps the main field of view, the extended field of view system mayprovide a backdrop for content displayed in the main field of view. Thebackdrop may be a lighting effect, for example, that is behind thecontent or near the content to provide context to the content. Thebackdrop may be a non-lighting effect where the pixels of thesee-through display (e.g. the pixels of a see-through LCD) are changedto be opaque or less transparent to provide a dark back drop behind thecontent or adjacent the content (e.g. to form the appearance of ashadow). In such embodiments, the extended field of view system mayoverlap the main field of view and the extended field of view system mayor may not extend past the edges of the main field of view.

In embodiments, a head-worn see-through display may be adapted toprovide a hybrid multi-FOV display. In an aspect, an optical system of ahead-worn see-through display may include a main image content optic forthe production of center-eye image content, an extended image contentoptic for the production of off-center-eye image content, and a combinerpositioned to present content to a user and through which the user viewsa surrounding environment, wherein each of the main image content opticand extended image content optic are positioned to project theirrespective image light to the combiner, which reflects the respectiveimage light to a user's eye. The combiner may directly reflect therespective image light to the user's eye. The combiner may indirectlyreflect the respective image light to the user's eye, wherein thecombiner may reflect the respective image light towards a collimatingpartial mirror. The center-eye image content and the off-center-eyeimage content may pass through at least one fold in the optical systembefore reflecting off of the combiner. The extended image content opticmay be mounted directly above the combiner such that the off-center-eyeimage content is directly projected to the combiner. The optical systemmay further include a processor adapted to coordinate a smoothdisappearing transition of world-locked content as the content movesfrom a field of view of the main image content optic to a field of viewof the extended image content optic and to an edge of the field of viewof the extended image content optic. The extended image content opticmay be an OLED, an LCD display, an array of LEDs, linear,two-dimensional, or curved. The extended image content optic maygenerate lighting effects corresponding to image content. The extendedimage content optic may include a lens system to modify the projection.The lens system may include an array of micro lenses.

In embodiments, a head-worn see-through display may be a hybrid displaywith a see-through panel. In an aspect, a head-worn see-through displaymay include a main image content display adapted to produce image lightand project the image light in a direction to be reflected by asee-through combiner such that it reaches an eye of a user, and asecondary image content display, wherein the secondary image contentdisplay is a see-through panel positioned directly in front of the eyeof the user and used to augment the visual experience delivered by themain image content display. The secondary display may provide content oreffects in an area outside of a main field of view that is produced bythe main image display. The area outside may be adjacent to the mainfield of view, surrounding the main field of view, or overlapping withthe main field of view. The secondary display may provide content oreffects in an area overlapping a main field of view produced by the mainimage display. The secondary display may be mounted on a combineradapted to reflect image light to an eye of the user or may be mountedvertically outside of an image light optical path established by themain image display. The head-worn display may further include aprocessor that is adapted to track an eye position of the user, theprocessor further adapted to alter a position of content as presented inthe secondary display. The altered position may substantially maintainan alignment of the main image display and the secondary image displayfrom the user's perspective as the user's eye moves. The see-throughpanel may be an OLED or an edge lit LCD.

In embodiments, a head-worn see-through display may be adapted to blendtypes of content. In an aspect, a head-worn see-through display mayinclude a field of view generated by an image display, wherein a userviews digital content in the field of view and sees through the field ofview to view a surrounding environment, and a processor adapted togenerate two types of content, wherein the two types of content arepresented in the field of view. The first type of content may beworld-locked content with a field of view position that is dependent ona place in the surrounding environment, wherein an appearance of thefirst type of content is diminished as it approaches an edge of thefield of view. The second type of content may not be world-locked,wherein the second type of content maintains a substantially constantappearance as it approaches the edge of the field of view. Thediminished appearance may include a reduction in resolution, a reductionin brightness, a reduction in contrast, regulated by a display driver,regulated by an application processor, or regulated by altered pixels ofa display that generates the field of view. The head-worn display mayfurther include a secondary field of view generated by the image displayin which the user views presented digital content and through which theuser sees the surrounding environment, the processor further adapted totransition the content from the field of view to the secondary field ofview. The appearance of the content in the secondary field of view isdiminished as compared to the appearance of the content in the field ofview. The secondary field of view may have a lower resolution than aresolution of the field of view. The secondary field of view may begenerated by reflecting image light onto a combiner that directs theimage light directly to an eye of the user, reflecting image light ontoa combiner that directs the image light towards a culminating partialmirror that reflects the image light to an eye of the user, an OLED thatprojects light onto a combiner, an LED array that projects light onto acombiner, an edge lit LCD that projects light onto a combiner, or asee-through panel positioned directly in front of the eye of the user.The panel is mounted on a combiner or vertically. The see-through panelis an OLED or an edge lit LCD. The processor may be further adapted topredict when the content is going to approach the edge of the field ofview and to base the appearance transition at least in part on theprediction. The prediction may be at least in part based on aneye-image.

In embodiments, a head-worn see-through display may be adapted to adjustan FOV alignment. The head-worn see-through display may include a hybridoptical system adapted to produce a main see-through field of view forthe presentation of content with high resolution and a secondarysee-through field of view for the presentation of content with lowerresolution, wherein the main and secondary fields of view are presentedproximate one another, a processor adapted to adjust the relativeproximity of the main and the secondary fields of view, and an eyeposition detection system adapted to detect a position of an eye of auser, wherein the processor adjusts the relative proximity of the mainand secondary fields of view based on the position of the eye of theuser. The secondary field of view may be produced on a see-through OLEDpanel positioned directly in front of the eye of the user, on asee-through edge lit LCD panel positioned directly in front of the eyeof the user, or on a see-through combiner positioned directly in frontof the eye of the user. The relative proximity may he a horizontalproximity or a vertical proximity. The relative proximity may define ameasure of overlap between the main and secondary fields of view or ameasure of separation between the main and secondary fields of view. Theeye position detection system may image the eye from a perspectivesubstantially in front of the eye, as a reflection off a see-throughoptic in a region including the main field of view, or as a reflectionoff a see-through optic in a region including the secondary field ofview.

When using head mounted displays (HMDs) (e.g. as part of an HWC 102) forpurposes such as augmented reality imaging, it is desirable to provide awide field of view (e.g. 60 degrees). However, in viewing a wide fieldof view with a head mounted display it should be recognized that viewingan image with a head mounted display is different than viewing an imageon a rigidly mounted screen in the environment (e.g. a televisionmounted on the wall or a movie theater screen). With a head mounteddisplay, as the user moves their head, the head mounted display and itsassociated display field of view moves as well in relation to thesurrounding environment. This makes it difficult for the user of an HMDto view the edge or corner of an image that is displayed with a widefield of view because head movements do not assist the user, eyemovements alone must be used to view the corner of the image. To improvethe viewing experience when using an HMD to view images displayed with awide field of view, the relationship between eye movement and headmovement that a person uses when viewing the surrounding environmentshould be substantially replicated. For example, a viewer would normallyturn his head, at least somewhat, when viewing an image with a widefield of view on a rigidly mounted screen such as in a movie theaterwhen looking towards an edge of the movie screen, as opposed to onlymoving his eyes towards the edge. The inventors have discovered thatcertain accommodations have to be made to provide comfortable andintuitive viewing of the areas towards the outer edges of a wide fieldof view in an HMD system. In embodiments, the content being displayed inthe wide field of view may not necessarily be world-locked (i.e. wherethe position of the content in the field of view is dependent on anobject's position in the environment such that the content appears tothe user as positionally connected to the environment) but may stillinclude a process that shifts a position of the presented content basedon a position or motion of the user's eye or head.

Because a head mounted display is worn on the head of the user,compactness is important to provide a comfortable viewing experience.Compact optical system typically include short focal length optics withlow f# to reduce the physical size. Optics with these characteristicsgenerally require a wide cone angle of light from the image source.Where wide cone angles are associated with image sources that emit imagelight from their front surfaces as, for example, in small displays ormicrodisplays such as OLED, backlit LCD, etc. These displays can emitunpolarized or polarized image light. The optical system receives theimage light from the image source and then manipulates the image lightto form a converging cone of image light that forms an image at the eyeof the user with an associated wide field of view. To enable the user tosimultaneously interact with the displayed image and the surroundingenvironment, it is advantageous to provide an undistorted and brightsee-thru view of the surrounding environment along with a bright andsharp displayed image. However, providing an undistorted and brightsee-thru view and a bright and sharp displayed image can be competingrequirements, especially when a wide field of view image is beingprovided.

For the purpose of viewing augmented reality imagery, it can bedesirable to provide a wide field of view of 50 degrees or greater.However, the design of compact optics with a wide field of view that issuitable for use in a compact head mounted display can be challenging.This is further complicated by the fact that the human eye is onlycapable of high resolution in a very narrow portion of the field of viewknown as the fovea and a much lower resolution at the periphery of thefield of view. To observe the whole area of a high resolution image, aperson must move their eyes over a wider field of view.

The inventors have discovered that optical systems are needed thatprovide high transparency to the surrounding environment to provide anundistorted and bright view of the surrounding environment while alsodisplaying bright and sharp images over a wide display field of view. Toprovide a comfortable viewing experience, the optical system should takeinto account how the user moves their eyes and their head to view theenvironment. This is particularly important when the user is viewingaugmented reality imagery.

Systems and methods in accordance with the principles of the presentinvention provide an HMD which displays images with wide fields of viewoverlaid onto a see-through view of the surrounding environment, with animproved see-through view and a high contrast displayed image. Anoptical system is provided that includes upper optics comprised of anemissive image source (e.g. OLED, backlit LCD, etc.), one or more lensesand a stray light trap, and non-polarized lower optics comprised of aplanar angled beam splitter and a curved partial mirror. The emissiveimage source provides image light comprised of one or more narrowspectral bands of image light. Wherein, one or more of the reflectivesurfaces on the beam splitter and the curved partial mirror is treatedto reflect a majority of incident light within the narrow spectral bandsand transmit a majority of incident light within the visible bandthereby providing a bright displayed image and a bright see-through viewof the surrounding environment (e.g. using a tri-stimulus mirror on thebeam splitter).

A stray light trap is also provided to enable higher contrast images tobe displayed in concert with a high transmission view of the surroundingenvironment. Where the stray light can come from various sourcesincluding: see-through light from the surrounding environment; imagelight that has been reflected back into the optics by the curved partialmirror; or light from below that has passed through the beam splitter.By trapping this stray light, the contrast of the displayed image asseen by the user is greatly improved.

A display operating mode is also provided for improved viewing of widefield of view images wherein the displayed image is laterally shiftedwithin the display field of view in correspondence to movements of theuser's head. Wherein the lateral shifting of the displayed image istriggered by detecting an eye movement followed by a head movement inthe same direction. The displayed image is then laterally shifted incorrespondence to and in an opposite direction to ensuing headmovements. The purpose of this mode is to enable the user to viewperipheral portions of the image without having to move their eyes tothe full extent of the wide displayed field of view. Thereby the userviews the wide field of view of the displayed image through acombination of eye movement and head movement to obtain a morecomfortable viewing experience.

Systems and methods in accordance with the principles of the presentinvention provide a head worn display with a high transmissionsee-through view of the surrounding environment and a high contrastdisplayed image that is overlaid onto the see-through view of thesurrounding environment. In this way, the systems and methods provide ahead worn display that is well suited for use with augmented realityimagery because the user is provided with a bright and sharp displayedimage while still being able to easily view the surrounding environment.The systems and methods also provide a wide field of view with asharpness that corresponds to the acuity distribution of the human eyewhen typical eye movement and head movement is taken into consideration.Where the wide field of view head mounted display can provide adisplayed field of view for example at least +/−25 degrees (50 degreeincluded angle). In addition, compact optics are provided with reducedthickness to improve a compact form factor of the head worn display.Operating modes are provided that take into account the viewingconditions of the head worn display where the display is attached to theuser's head.

FIG. 169 shows a cross sectional illustration of an example opticsassembly 16900 for a head worn display. The optics assembly 16900include upper optics 16903 comprised of an emissive image source 16910,one or more lenses 16920 and a light trap 16930, and lower optics 16907comprised of an angled beam splitter 16950 and a curved partial mirror16960. The emissive image source 16910 provides image light 16940, withimage content, that is optically manipulated by the lenses 16920 and thecurved partial mirror 16960 to form a wide field view that is presentedto a user's eye in the eyebox 16970. Where the eyebox is defined as theregion wherein the user's eye can see the displayed image. The opticsare folded to make the optics assembly 16900 more compact, so that theoptics have a first optical axis 16946 that extends perpendicularly fromthe emissive image source 16910. The angled beam splitter 16950redirects a portion of the image light 16940 by reflection so that theimage light 16940 passes out along a second optical axis 16943. Thecurved partial mirror 16960 reflects a portion of the image light 16940so that it passes back along the second optical axis 16943 and towardsthe eyebox 16970. Simultaneously, scene light 16973 from the surroundingenvironment is transmitted by the curved partial mirror 16960 and theangled beam splitter 16950 to provide a see-through view of thesurrounding environment to the eyebox 16970. As such the curved partialmirror 16960 acts as a combiner wherein the user sees the displayedimage provided by the image light 16940 overlaid onto the see-throughview of the surrounding environment provided by the scene light 16973.

The emissive image source 16910 can be any type of luminous display thatdoesn't require supplemental light to be applied (e.g. a transmissivefront light as described herein elsewhere) within the upper optics 16903including: an OLED, a backlit LCD, a micro-sized LED array, a laserdiode array, edgelit LCD or a plasma display. Typically an emissivedisplay provides image light with narrow wavelength bands of lightwithin the visible range. For example, for a full color display thebands can include a red, green and blue band with full width halfmax(FWHM) wavelengths of 615-635, 510-540 and 450-470 nm respectively. Inaddition, the emissive image source 16910 provides a wide cone of imagelight (e.g. 100 or more degrees). There are a number of advantagesassociated with using an emissive image source 16910 that has a widecone angle in that, the optical system can be designed with a shorterfocal length and a faster f# (e.g. 2.5 or faster) which enables theoptics to be much more compact. In addition, by eliminating the need foran illumination system to apply light to the front surface of the imagesource such as is typically required for a reflective image source likean LCOS or a DLP, the overall size of the upper optics can be reducedsubstantially.

In embodiments, to provide a high transmission (e.g. greater than 50%transmission of scene light to the eye) see-through view of thesurrounding environment, the lower optics are a non-polarized design,wherein the optical surfaces allow some portion of unpolarized visiblelight to be transmitted. This is to avoid the greater than 50% losses oflight that occur when an absorptive polarizer or reflective polarizer isused in transmission along the optical path of scene light 16973.Instead, the reflective surfaces on the angled beam splitter 16950 andthe curved partial mirror 16960 are treated to be partially reflective.Where the partially reflective treatment can be a base partial mirrorthat has a relatively uniform level of reflectivity across the entirevisible range, or the partially reflective treatment can be a notchmirror that provides higher levels of reflectivity in one or more narrowwavelength bands within the visible range that have been selected tomatch the output bands of the emissive image source and higher levels oftransmission in the wavelengths between the narrow wavelength bands(e.g. as described herein elsewhere). The partially reflective treatmentcan be a coating such as a multilayer coating, a phase matchednanostructure or a film such as a multilayer film or a coated film thathas partial mirror properties or notch mirror properties.

By using non-polarized lower optics 16907 in the portion of the opticswhere a see-through view of the surrounding environment is provided,there is an added benefit in that chromatic aberrations are avoided whenviewing a polarized image source in the environment such as a liquidcrystal television or computer monitor or natural sources like cloudsand reflections that could be very distracting to the user. Thesechromatic aberrations typically take the form of rainbow patterns withbright colors that can be very distracting to the head worn experience.The chromatic aberrations are caused by interference between thepolarized light of the polarized image source and any polarizers orcircular polarizers that are present in the see-through portion of theoptics. As a result, the systems and methods described providenon-polarized optics in the see-through portion of the optics to enablethe user to view polarized image sources such as liquid crystal computermonitors without being exposed to rainbow patterns while wearing a headworn display.

With a high transmission see-through view of the surroundingenvironment, a high level of scene light 16973 passes through the loweroptics on the way to the eyebox 16970. This opens up the possibility fora loss of contrast in the displayed image due to stray light from aportion of the scene light 16973 being reflected by the angled beamsplitter 16950 back to the emissive image source 16910, and also from aportion of the image light 16940 being reflected by the angled beamsplitter 16950 back toward the emissive image source 16910. The combinedstray light from the portions of the scene light 16973 and the imagelight 16940 being reflected back to the emissive image source 16910 isthen scattered off of the sidewalls in the upper optics 16903 andreflected by the surface of the emissive image source 16910 so that itjoins the image light 16940 that is presented to the eyebox 16970 forviewing by the user. Since this stray light does not have image content,the net effect is that the contrast in the displayed image is reduced.To reduce the stray light from these two sources, a light trap 16930 isprovided.

FIG. 170 shows an illustration of the light trap 16930 operating toreduce stray light. The light trap 16930 is comprised of a sandwichstructure including quarter wave films 17032 and 17034 on either side ofa linear polarizer film 17033. The sandwich structure can be looselyconnected or laminated together with adhesive layers. The light trap16930 functions by allowing unpolarized image light 17025 from theemissive image source 16910 to pass through quarterwave film 17032,which doesn't affect the image light 17025 because it is unpolarized.The image light 17025 then passes through the polarizer 17033, whichcauses the image light to become linearly polarized. The linearlypolarized image light then passes through quarterwave film 17034, whichcauses the image light to become circularly polarized image light 17026.A portion of the circularly polarized image light 17026 is reflectedtoward the curved partial mirror 16960 by the angled beam splitter16950, while another portion of the circularly polarized image light istransmitted by the angled beam splitter 16950 to become faceglow. Thecurved partial mirror 16960 reflects a portion of the circularlypolarized image light 17026 back toward the angled beam splitter 16950while transmitting apportion that becomes eyeglow. From the circularlypolarized image light 17026 that passes back toward the angled beamsplitter 16950, a portion is transmitted to the eyebox 16970 and afurther portion is reflected by the angled beam splitter 16950 so thatit passes toward the emissive image source 16910. However when thereturning circularly polarized image light 17026 passes through thequarterwave film 17034, it is transformed into linearly polarized lightwith the opposite polarization orientation compared to the image light17025 so that the polarizer 17033 absorbs the returning light. As suchthe portion of the image light that is reflected back toward theemissive image source 16910 can be essentially eliminated by the lighttrap 16930 considering that typical absorptive polarizers absorbapproximately 99.99% of light with the opposite polarization state.

Scene light 17045 is unpolarized and is transmitted by the curved beamsplitter 16960. When the unpolarized scene light 17045 encounters theangled beam splitter 16950, a portion is transmitted toward the eyebox16970 to provide a see-through view of the environment and a portion isreflected toward the emissive image source 16910. The unpolarized scenelight 17045 passes through the quarterwave film 17034 unchanged. As thescene light passes through the polarizer 17033 it becomes polarizedlight. The scene light then becomes circularly polarized scene light17046 as it passes through quarterwave film 17032. The circularlypolarized scene light 17046 is reflected by the surface of the emissiveimage source 16910. This returning circularly polarized scene light17046 is transformed into polarized scene light with an oppositepolarization state when it passes back through quarterwave film 17032,which is then absorbed by the polarizer 17033.

The net effect of the light trap 16930 is that stray light fromreturning image light and scene light is essentially eliminated and as aresult, the contrast in the displayed image is greatly increased. Thisis particularly important when using the head worn display in a brightenvironment where the incoming scene light 17045 can be substantial. Byusing a light trap 16930 with a sandwich structure comprised ofquarterwave films 17032 and 17034 on either side of a linear polarizerfilm 17033, stray light from unpolarized light 17025 and 17045 coming inopposing directions can be effectively trapped. The effect on theportion of the image light 17025 that is reflected by the angled beamsplitter 16950, is reflected by the curved partial mirror 16960 and istransmitted by the angled beam splitter 16950 so that it becomes thedisplayed image that is viewed by the user, is that this image light16940 is circularly polarized light. In addition, since the image light17025 passes through a polarizer film 17033, there is a reduction inbrightness of approximately 50%. However the increase in contrast ismuch higher, so that the perceived image quality of the displayed imageis greatly improved especially in a bright environment. The inventorshave performed measurements of the effectiveness of such a light trappositioned above an OLED display surrounded by a black textured plasticframe. Wherein the quarter wave film was selected to have a retardationlevel that provides excellent extinction of the stray light after itpasses through the quarterwave film twice without imparting a color biasto the remaining stray light. The result was that light reflected fromthe OLED display surface was reduced by 117X and light reflected fromthe black textured plastic was reduced by 6X.

The light trap 16930 can also be simplified to be a circular polarizerby eliminating one of the quarter wave films. In this case, the lighttrap 16930 works on only one of the unpolarized stray light sources. Ifquarterwave film 17032 is eliminated, the light trap 16930 traps onlystray light from the image light 17025 and the scene light 17046reflected back toward the image source 16910 is then polarized.Alternately, if quarterwave film 17034 is eliminated, the light trap16930 traps only stray light from the scene light 17045 and the imagelight 17026 is then polarized.

In an alternative embodiment, the light trap 16930 can be positioned onthe surface of the image source 16910. The light trap can be a polarizer17033 sandwiched between quarter wave films 17032 and 17034 to trapstray light from both scene light 17045 and image light 17025 that isreflected back toward the image source 16910. By positioning the lighttrap 16930 directly on the surface of the image source 16910, straylight from scene light 17045 is trapped very efficiently becausebirefringence in the lenses 16920 don't affect the polarization state ofthe circularly polarized scene light 17046. As such, the light trap16930 can be a circular polarizer that is positioned on the image source16910 with the quarter wave film of the circular polarizer against thesurface of the image source 16910 to trap just the stray lightassociated with the scene light 17045 as previously described herein.The light trap 16930 can be sized to cover the surface of the imagesource 16910 in addition to covering adjacent reflective portions of theimage source package or the adjacent housing to trap stray lightassociated with reflected light from these surfaces.

To trap stray light from image light 17025 that is reflected back towardthe image source 16910, a second circular polarizer (e.g. comprised ofpolarizer 17033 and quarter wave film 17034) can be positioned betweenthe lenses 16920 and the lower optics, wherein the quarter wave film17034 of the second circular polarizer is positioned to face the loweroptics. The polarization axis of the first circular polarizer should bealigned with the polarization axis of the second circular polarizer totransmit the most image light 17025. This second circular polarizerprovides an efficient light trap for stray light from image light 17025that is reflected by the partial mirror 16960 and the angled beamsplitter 16950 back toward the image source 16910. However, if a firstand second circular polarizer are included, birefringence in the lenses16920 in the upper optics will affect the brightness uniformity andcontrast uniformity of the image seen by the user. This is because theimage light 17025 will be polarized by the first circular polarizer, theimage light will then pass through the lenses 16920 where anybirefringence present will cause portions of the image light to becomeelliptically polarized. The elliptically polarized image light will thenpass through the second circular polarizer where the ellipticallypolarized portions of the image light will be filtered in correspondenceto the degree of elliptical polarization present. If the lenses 16920have low birefringence (e.g. <50 nm retardation), using two circularpolarizers will provide an image with barely noticeable degradation ofbrightness uniformity and contrast uniformity, however if thebirefringence is high then the brightness uniformity and contrastuniformity will be noticeably degraded.

Table 1, below, shows a comparative analysis of a variety ofnon-polarized partially reflective treatments for the angled beamsplitter 16950 and the curved partial mirror 16960 where all the numbersare presented in terms of % of the image light 17025 emitted by theimage source 16910. This analysis shows the effects of using notchmirror treatments compared to base partial mirror (i.e. a partial mirrorthat reflects all visible wavelengths substantially equally) treatmentson the angled beam splitter 16950 and the curved partial mirror 16960along with the effects of the light trap 16930. Phase matchednano-structures that reflect narrow wavelength bands of light can beprovided as an embossed film or as a molded in structure on an opticalsurface, to provide a notch mirror treatment, but they are not shown inTable 1. In this analysis, the reflectivities of the angled beamsplitter 16950 and the curved partial mirror 16960 have been chosen todeliver at least 50% “See-through light to the eye” (this is scene light16973 that reaches the eyebox 16970) with at least 20% “See-throughlight at the wavelengths of the image light”, which takes into accountthe narrow band of reflectivity provided by any notch mirror treatmentson the reflective surfaces. Case 1 includes triple notch mirrortreatments (also known as a tristimulus notch mirror for reflectingnarrow bands of red, green and blue light] to the angled beam splitter16950 and the curved partial mirror 16960 and it does not include alight trap 16930. In this analysis, the notch mirror was assumed toreflect at a selected reflectivity % within a 20 nm wide band for eachcolor (for example the triple notch mirror can provide high reflectivityin the following bands: 450-470 nm for blue, 515-535 nm for green,615-635 nm for red) and transmit the remaining visible light at 95%.Case 2 includes triple notch mirror treatments to the angled beamsplitter 16950 and the curved partial mirror 16960 along with a lighttrap 16930. Case 3 includes a base partial mirror treatment on thecurved partial mirror 16960 arid a triple notch mirror treatment on theangled beam splitter 16950 along with a light trap 16930. Case 4includes a base partial mirror treatment on the angled beam splitter16950 and a triple notch mirror treatment on the curved partial mirror16960 along with a light trap 16930. Case 5 includes base partial mirrortreatments on both the angled beam splitter 16950 and the curved partialmirror 16960 along with a light trap 16930.

Case Number 1 2 3 4 5 Coating on beam splitter Tristim Tristim TristimSimple Simple notch notch notch partial partial mirror mirror mirrormirror mirror Coating on curved partial mirror Tristim Tristim TristimTristim Simple notch notch notch notch partial mirror mirror mirrormirror mirror Quaterwave/polarizer sandwich trap No Yes Yes Yes 20 forlight reflected back to display Beam splitter reflectivity image light50 50 60 30 75 (%) Beam splitter transmission overall (%) 83 83 80.6 6528 Curved partial mirror image light 80 80 33 75 67 reflectivity (%)Curved partial mirror image overall 75.8 75.8 62 77 15 transmission (%)Reflectivity of display panel (%) 15 15 15 15 15 Image light to the eye20.0 8.4 3.3 6.1 1.8 See-thru light to the eye 62.9 62.9 50.0 50.1 50.3Eyeglow 10.0 4.2 16.9 3.2 5.6 Faceglow 50.0 21.0 16.8 27.3 31.5 Lightfrom below reflected toward eye 12.0 12.0 14.4 30.0 20.0 Image lightback to panel 20.0 0.00084 0.000499 0.000284 0.00005 See-thru light withimage light 10.0 4.2 15.6 3.2 5.6 wavelengths back to panel See-thrulight with image light 1.5 0.000063 0.000234 4.738-05 0.00008wavelengths back to panel and reflected back toward eye See-thru lightwith image light 20.1 20.1 31.0 25.2 50.3 wavelengths to eye Ratio imagelight to eye-image light 7 10000 6667 21667 37500 back to panel Ratioimage light to eye See-thru light 13 133333 14194 130000 20896 withimage light wavelengths back to panel and reflected back into system

The effects of the light trap 16930 on image contrast can be seen in thetwo rows at the bottom of Table 1 that relate to image contrast as shownby ratios of the “Image light to the eye”, which represents thedisplayed image brightness, divided by the “light back to the imagesource” where the light back to the image source comes from either theimage light being reflected back to the image source or from scene lightbeing reflected back to the image source. In both sets of numbers, theratio is dramatically higher (1000× or more) in Cases 2-5 where there isa light trap 16930 compared to Case 1 where there is not a light trap.The light loss produced by having a light trap can also be seen in thenumbers for the “Image light to the eye” wherein Case 1 showsapproximately 2× higher numbers indicating a brighter displayed image.

The effects of the notch mirror treatments on the numbers for the “Imagelight to the eye” (image light 16940) and “See-through light to the eye”(scene light 16973) can be seen by comparing Cases 2-4 which havevarious combinations of tristimulus notch mirror treatments to Case 5which has base partial mirror treatments on the angled beam splitter16950 and the curved partial mirror 16960. The tristimulus notch mirrortreatment on one or both reflective surfaces increases the portion ofimage light 16940 that is delivered to the eyebox 16970 while alsoincreasing the portion of scene light 16973 that is provided to the eye.Using base partial mirror treatments on both the angled beam splitter16950 and the curved partial mirror 16960 reduces the efficiency of theoptics to deliver image light to the user's eye by a factor ofapproximately 2× to 4.5×. It should be noted that if either the angledbeam splitter 16950 or the curved partial mirror 16960 included apolarizer (absorptive or reflective), only about 42% of the scene lightwould be transmitted to the user's eye based on typical transmission %of unpolarized light by polarizers. And if one of the surfaces is apolarizer and the other is a 50% partial mirror, only about 21% of thescene light would be transmitted to the user's eye.

Other light losses are also shown by the numbers in Table 1. “Eyeglow”is the portion of image light 16940 that is transmitted by the curvedpartial mirror 16960. “Faceglow” is the portion of image light that istransmitted downward by the angled beam splitter 16950. Thedetermination of which Case is better in terms of eyeglow and faceglowfor a given head worn display will depend on whether there are othercontrols present to mitigate eyeglow or faceglow. If there are eyeglowcontrols present, then Case 3 may be the best choice because thefaceglow is lower. If there are faceglow controls present than Case 4may be the best choice because it has lower eyeglow.

In general, Case 2 with tristimulus notch mirror treatments on both theangled beam splitter 16950 and the curved partial mirror 16960 has agood combination of characteristics for providing a bright and highcontrast image to the user's eye along with a high see-throughtransmission. This is because Case 2 has relatively good numbers forefficiency for delivering image light to the eye, high transmissionsee-through, low eyeglow, low faceglow, acceptable see-through at thewavelengths of the image light and excellent contrast.

Tristimulus notch mirror treatments can be obtained that reflect Spolarized light more than P polarized light. However, given the narrowbands of reflection provided by the tristimulus notch mirror treatment,the transmitted portion of the light can be substantially non-polarizedand as such still provide transmission of scene light that is over 50%and provide a view of polarized light sources that do not containchromatic aberrations such rainbows. Under this scenario, Case 4 can bemore efficient for delivering image light to the eye and providing highsee-through transmission.

In many uses cases, such as for example augmented reality imaging, it isdesirable to use a head mounted display that provides a wide field ofview, e.g. greater than 40 degrees. However it can be difficult todesign any type of optics that provide uniformly high MTF for auniformly sharp image over the entire wide field of view. As a result,the optics can be very complicated and the physical size of the opticscan become unsuitably large for use in a head mounted display. To avoidthis problem, it is important to understand the acuity of the human eyein the peripheral portions of the field of view and to understand theangular range of eye movement typically used before a person moves theirhead.

FIG. 172 shows a chart of the acuity of a typical human eye relative tothe angular position in the field of view (S. Anderson, K Mullen, RHess; “Human peripheral spatial resolution for achromatic and chromaticstimuli: limits imposed by optical and retinal factor?, Journal ofPhysiology (1991), 442, pp 47-64). The fovea at the center of the humaneye provides very high acuity over an angular range of approximately 2degrees. The acuity then drops off rapidly as the angular position inthe field of view (also known as eccentricity) increases. In addition,the chromatic acuity is substantially lower than the achromatic acuity.As shown in FIG. 172, the achromatic acuity goes from approximately 50cycles/degree at the fovea to 5 cycles/degree at 15 degrees and thechromatic acuity goes from approximately 30 cycles/degree at the foveato 3 cycles/degree at 15 degrees. FIG. 173 shows a chart of the typicalacuity of the human eye vs the eccentricity in a simplified form thathighlights the dropoff in acuity with eccentricity along with thedifference between achromatic acuity and chromatic acuity.

However, the acuity of the eye that is experienced by the user has totake into account the rapid movements of the eye within the field ofview. These rapid movements of the eye effectively expand the highacuity portion of the field of view seen by the user. In an augmentedreality application, movement of the head by the user must also be takeninto account. When the user perceives an object near the edge of theeye's field of view, the user first moves their eyes toward the objectand then moves their head. These combined movements enable the user toview a wider field of view while also making it more comfortable to viewan object at the edge of the field of view by reducing the angularmovement of the eyes. Human's tend to only move their eyes a limitedamount before they move their head. FIGS. 174A and 174B show typicalexamples of eye movements and head movements given in charts showingangular movements in radians vs time for a variety of situations (ADoshi, M Trivedi; “Head and eye gaze dynamics in visual attention andContext Learning”, 2009 IEEE, 978-1-4244-3993-5/09, pp 77-84). As seenin the data given in the lower panel of FIG. 174A, the user's head tendsto move quickly after an eye movement to recenter the eye within thefield of view so that the head and the eye have the same angle. FIG.174B shows the converse situation in which the head moves first followedby an eye movement. Angular disparities between the eye and the headtend to be limited to less than approximately 0.25 radians (which isequal to approximately 15 degrees) except for very brief excursions.This is different from a head movement that occurs when a person reactsto a sound wherein the eyes and the head move together with minimaldisparity, as in the top panel of FIG. 174A. If the user wants to lookat an object that is more than approximately 15 degrees from thedirection the head is pointed, the user will first move their eyes andthen move their head, as seen in the lower panel of FIG. 174A, to reducethe angular disparity between the eyes and the head to less than 15degrees to look at the object. This relationship between the movement ofthe eyes and the movement of the head is important to take into accountwhen designing and operating a head worn display with a wide displayfield of view. Based on the acuity of the human eye and the movement ofthe eye relative to the movement of the head, sharp images with highresolution and high contrast are needed within the central +/−15 degreeto +/−20 degree portion of the display field of view to provide the userwith an image that is perceived as sharp and high contrast. This is thecentral region of the display field of view wherein the user will movetheir eyes to look at the image with the fovea. Outside of this regionof the display field of view, the displayed image does not have to be assharp because the user will not typically look directly at that regionof the display field of view. Instead for example, to view an augmentedreality object that is located 30 degrees from the center of thedisplayed field of view, the user will move their eyes approximately 15degrees toward the object and then turn their head the remaining 15degrees toward the object. If the augmented reality object is worldlocked (i.e. where the object is displayed in a constant positionrelative to real objects in the surrounding environment), as the usermoves their head, the augmented reality object will move toward thecenter of the displayed field of view and as such it will move into thecentral sharp region of the display field of view.

FIG. 175 is a chart that shows the effective relative achromatic acuity,compared to the acuity of the fovea, provided by a typical human eyewithin the eye's field of view when the movement of the eye is included.Within the +/−15 degree portion of the field of view that is viewed withthe fovea by moving the eyes, the relative acuity is equal to thatprovided by the fovea. Beyond the portion of the field of view that isviewed with the fovea, the acuity decreases at the rate associated witheccentricity in the eye as shown in FIG. 173. This acuity chartcorresponds to the sharpness distribution that needs to be provided by ahead worn display with a wide field of view. As long as the displayedimage is provided with a relative sharpness that is above the acuitydistribution shown in FIG. 175, the human eye will perceive thedisplayed image to be uniformly sharp. This is because when an image ispresented with a field of view that is wider than the portion of thefield of view that can be comfortably viewed by the fovea, the acuity ofthe eye is substantially decreased. For example, based on the acuitychart in FIG. 175, an image can be presented with a central sharp zonethat is +/−15 degree to a +/−20 degree in size and as long as the imagesharpness decreases to no less than 20% of the sharpness of the sharpzone by approximately +/−25 degrees, the image will be perceived by theuser as being uniformly sharp. FIG. 176 is a chart that shows theminimum design MTF vs angular field position needed to provide auniformly sharp looking image in a wide field of view displayed image.In this figure the design MTF is given as a spatial modulation at 20%MTF relative to Nyquist, where Nyquist MTF is 100% and reduced MTF isless. The chart shows a uniform design MTF of 100% Nyquist across thecentral sharp zone (+/−15 degrees) and a rapidly decreasing design MTFin the peripheral zone (greater than 15 degrees). By providing a reduceddesign MTF in the outer portions of the angular field, the optics can begreatly simplified, thereby reducing cost and reducing the overall sizeof the optics.

FIG. 177 is a chart that shows the relative MTF needed to be provided bythe display optics for a wide field of view display to provide asharpness that matches the acuity of the human eye in the peripheralzone of the display field of view, wherein the resolvable sharpness foroptics is determined to be the spatial frequency at which the MTF is20%. In the figure, simple two point MTF curves (100% MTF and 20% MTF)are shown for a variety of angular field positions in the display fieldof view: 0 to 15 degrees (this is the top right curve), 20 degrees, 25degrees, 30 degrees, 35 degrees, 40 degrees, 45 degrees and 50 degrees(this curve is the bottom left curve). These curves show the minimum MTF(from FIG. 176) that needs to be provided across the display field ofview to match the acuity of the human eye. As can be seen, this resultshows that the MTF for wide field of view optics can drop offsubstantially in the outer portions of the display field of view. Forexample, the MTF of the wide field of view optics can be above 20% atthe Nyquist frequency of the image source in the central sharp zonewhile the MTF can be much lower in the peripheral zone, such as 2% or20% at ½ the Nyquist frequency. It should also be noted that since thechromatic acuity of the human eye is lower than the achromatic acuity,substantial lateral color (e.g. 5 pixels or more at 25 degrees) can bepresent in the peripheral regions of the wide field of view displayedimage and the lateral color will not be noticeable. Thus, lateral colorin the peripheral regions of the displayed wide field of view imagecontribute more to reducing the perceived sharpness of the image but thelow acuity of the eye in the peripheral regions makes the loss insharpness imperceptible. Similarly, the low acuity of the human eye inthe peripheral regions makes distortion less perceptible in theperipheral regions. The combination of the loss of acuity and reductionin chromatic acuity that makes distortion less noticeable all addtogether to a reduce need for image quality in the peripheral regions ofthe display field of view.

As an example, FIG. 171 shows an illustration of a simple optical systemthat provides a 60 degree display field of view (i.e. +/−30 degrees fromcenter). This includes an emissive image source 16910, a single lenselement 16920, an angled beam splitter 16950 and a curved partial mirror16960 as previously described herein. The optical system provides adisplayed image to eyebox 16970 with a displayed field of view ofapproximately 60 degrees included angle. Simultaneously, the user isprovided with a see-through view of the surrounding environment throughthe angled beam splitter 16950 and the curved beam splitter 16960,wherein the see-through field of view can be larger than the displayfield of view by enabling a view of the surrounding environment throughareas adjacent to or extensions of the angled beam splitter 16950 andthe curved partial mirror 16960. FIG. 178 shows a modeled MTF curveassociated with the optical system of FIG. 171 wherein MTF curves for avariety of different angular positions within the display field of vieware shown. The MTF curve for the 15, 6 degree position (expressed inhorizontal, vertical degrees within the field of view) in the displayfield of view is indicated with an arrow in FIG. 178, where it can beseen that the 15 degree MTF curve ends at 20% MTF at the Nyquist pointfor the image source which in this case corresponds to the right handend of the spatial frequency axis or 75 cycles/mm. The MTF curves belowthe indicated 15, 6 degree MTF curve are 30 degree MTF curves. For the30 degree points in the display field to have the same perceivedsharpness as the 15 degree point in the display field, according to FIG.176 the 30 degree MTF curve needs to be have at least 20% MTF at 7.5cycles/mm (10% of Nyquist). It can be seen that all of the 30 degree MTFcurves shown in FIG. 178 are easily above 20% MTF at 7.5 cycles/mmpoint, so as such the image will be perceived as sharp in the peripheralregions by the human eye, when limited movements of the human eye areconsidered. Thus, even though the MTF curves shown in FIG. 178corresponding to the peripheral angular positions in the display fieldof view do not meet the Nyquist performance conditions for this displayof 20% MTF at 75 cycles/mm, the peripheral points in the field of viewwill still be perceived by the user as providing the same level ofsharpness as that provided by the central angular points in the field ofview.

FIG. 179 is an illustration of a resolution chart wherein the sharpnessof the image has been reduced by blurring the peripheral portion of theimage to simulate an image from optics that provide a central sharp zoneof +/−15 degrees with a peripheral zone that is less sharp. Lookingdirectly at different portions of the image, it can be seen that theouter portions 17910 are much less sharp than the central zone 17920.However, if the image is viewed at a distance where the central zone17920 between the vertical bars occupies approximately +/−15 degrees inthe viewer's field of view, the image will appear to be uniformly sharpto the outer edge as long as the viewer keeps their gaze inside theinner edge of the vertical bars.

As a result, the systems and methods described herein in accordance withthe principles of the present invention can be used to design any typeof optics for head mounted displays with a wide field of view includingoptics with a beam splitter, optics with a waveguide or projected opticswith a holographic optical element, wherein a central sharp zone isprovided that delivers a level of MTF that corresponds to the acuity ofthe fovea and a peripheral zone adjacent to the central sharp zone thatprovides a reduced level of sharpness in correspondence to the acuity ofthe human eye when limited movement of the eye is considered. Inembodiments, the central sharp zone comprises a +/−15 degrees about theoptical axis (30 degree included angle] and the peripheral zone extendsbeyond the central sharp zone to the edge of the field of view of thedisplayed image. The MTF in the central sharp zone should be above 20%at the Nyquist level of the display to provide a sharp image. The MTF inthe peripheral zone can reduce with increasing angle at a rate that isless than the decrease in acuity of the human eye as the eccentricityincreases. For example, if the peripheral zone extends from +/−15degrees to +/−30 degrees (60 degree included angle], the MTF can be aslow as 10% of the Nyquist spatial modulation at 20% MTF. By limiting theangular zone where high MTF is required and reducing the design MTF inthe peripheral zone, the optics can include fewer elements and simplerelements with lower cost materials, thereby reducing the overall cost ofthe optics, in addition, the optics can be made more compact to enablethe wide field of view optics to better fit into the head mounteddisplay. This effect is shown by the compact optics shown in FIG. 171which as previously stated herein provide a 60 degree field of viewwhile including a single plastic field lens, a beam splitter and acurved partial mirror. Wherein the treatments for the beam splitter andthe curved partial mirror have been discussed previously herein toprovide high see-through with a non-polarized lower to eliminaterainbows when looking at a polarized light source. And in addition, alight trap can be added to the compact optics to increase contrast asalso discussed previously herein.

The systems and methods described herein in accordance with theprinciples of the present invention can be used for making compactoptics for a head mounted display with a wide display field of view thathas improved contrast and has a high transparency for the see-throughview of the surrounding environment. By using an emissive display, theneed for a frontlight is eliminated thereby reducing the space betweenthe emissive image source and the lower optics. By limiting the high MTFzone to a central sharp zone surrounded by a lower MTF peripheral zone,the number of lens elements required to display a wide field of view isreduced, thereby also reducing the size of the optics. As shown in FIG.171, a 60 degree field of view is possible with only one or two lenselements in the upper. As a result, the height of the optics can bereduced.

In embodiments, the emissive image source 16910 and the angular size ofthe display field of view are selected so that a single pixel in theemissive image source 16910 subtends an angle in the displayed imagethat is smaller than the achromatic acuity of the fovea of the humaneye, so that black and white portions of displayed images don't have apixelated look when viewed by the user. This provides the user with animage that has smooth lines and curves without the jagged look producedwhen individual black and white pixels can be resolved. For example,based on the data shown in FIGS. 172 and 173, the human eye has anachromatic acuity of approximately 50 cycles/degrees, for adjacent blackand white pixels to not be separately resolvable in the sharp zone of adisplayed image that includes 1920×1080 pixels (1080p), the displayedfield of view should be less than 38×22 degrees or 43 degrees diagonal.

In embodiments, the emissive image source 16910 and the angular size ofthe display field of view are selected so that a single pixel in theemissive image source 16910 subtends an angle in the displayed imagethat is smaller than the chromatic acuity of the human eye, so thatcolored portions of displayed images don't have a pixelated look whenviewed by the user. This provides the user with an image that has smoothlines and curves on colored areas without the jagged look produced whenindividual colored pixels can be resolved. For example, based on thedata shown in FIGS. 172 and 173, the human eye has a chromatic acuity ofapproximately 30 cycles/degrees, for adjacent colored pixels to not beseparately resolvable in the sharp zone of a displayed image thatincludes 1920×1080 pixels, the displayed field of view should be lessthan 64×36 degrees or 73 degrees diagonal.

In embodiments, the emissive image source 16910 and the angular size ofthe display field of view are selected so that the subpixels (typicallyeach full color pixel includes adjacent red, green and blue subpixels,and the relative brightness of the subpixels together determine theperceived color of the pixel) that makeup each pixel in the emissiveimage source subtend an angle that is smaller than can be resolved bythe human eye so that each pixel appears to be comprised of a singlecolor and the subpixels are not visible to the user. This provides theuser with an image is comprised of consistent blocks of colors withoutthe speckled look that can be perceived when individual subpixels can beresolved. For example, based on the data shown in FIGS. 172 and 173, thehuman eye has an achromatic acuity of approximately 50 cycles/degrees,for the subpixels to not be resolvable in an image that includes1920×1080 pixels, the displayed field of view is less than 115×64degrees or 131 degrees diagonal.

In embodiments, the optics include a telecentric zone in the image lightoptical path wherein lens elements can be moved relative to one anotherto affect a change in focus distance without changing the magnificationof the displayed image. Changes in focus distance can be accomplished ina variety of ways in a head mounted display by changing the spacingbetween optical elements. For example, focus adjustments can beaccomplished by moving the image source in relation to the remainder ofthe optical system. However, in a display system with a wide field ofview, the image light 16940 emitted by the emissive image source 16910must be expanded in area to fill the area of the curved partial mirror16960 which establishes the angular size of the display field of view asseen from the eyebox 16970 as shown in FIG. 171. To this end, the raybundles between the emissive image source 16910 and the lens element16920 are rapidly diverging (e.g. a 100 degree or more included angle).Because of the diverging ray bundles emitted by the emissive imagesource 16910, any change in spacing between the emissive image source16910 and the lens element 16920 done to change the focus distance orfocus quality is accompanied by a change in the visual size of thedisplayed image seen by the user. In a head mounted display that ispresenting augmented reality imagery, particularly when focusadjustments are done automatically as the user moves or as augmentedreality objects move, it is important that the visual size of theaugmented reality objects be consistent with the movements to providecomfortable viewing conditions for the user. Changes in the visual sizeof displayed image can also cause the image to be clipped by portions ofthe housing that are adjacent to the optics so that the edges of thedisplayed image are not viewable from the eyebox or the effective sizeof the eyebox is reduced. As such, the ability to makes changes in thefocus distance for the displayed image or portions of the displayedimage without changing the visual size of the image is an importantfeature for a head mounted display that is used to display augmentedreality imagery. The telecentric zone can be provided in a number oflocations within the optics such as between lenses in the upper opticsor between the upper and lower optics. FIG. 171 shows a telecentric zone17140 between the upper and lower optics where the central rays in eachray bundle are parallel. Within this telecentric zone 17140, focusadjustments can be made by moving the lens element 16920 and emissiveimage source 16910 as a first unit relative to a second unit comprisedof the angled beam splitter 16950 and curved partial mirror 16960 tochange the focus. As an example, for the optics shown in FIG. 171, areduction in spacing between the upper optics 16903 and lower optics16907 of 0.5 mm can provide a change in focus distance from infinity to1 meter (this is the same as adding 1 diopter corrective lens behind theoptics). This ability to adjust focus distance can be used to fine tunethe sharpness of the displayed image for the user or to change theapparent distance that the displayed image is presented to the user.Where changes in the apparent distance of the displayed image can beused for augmented reality use cases where the displayed image ispresented at a distance that matches an object in the environment or ata specific distance such as at arm's length.

Manual mechanisms such as screws or cams can be positioned to change thespace in the telecentric zone by moving the relevant optical elements.Where manual adjustments are useful for adjusting focus duringmanufacturing or to enable users to fine tune focus for their ophthalmicpower prescription. Electronic actuators can be mounted to automaticallyadjust the spacing in the telecentric zone for augmented realityapplications or for mode changes that include a change in focusdistance.

In embodiments, a telecentric zone may not be provided or it may be onlynearly telecentric and focal plane adjustments may be made by movingoptical elements and also adjusting, digitally, the content tocompensate for a magnification effect caused by the shifting elements inthe non-telecentric zone.

In embodiments, a mode for viewing a wide angle displayed image (e.g.greater than 50 degrees included angle) with a head mounted display ofany type is provided wherein the image is moved laterally within thedisplay field of view in correspondence to a detected eye movementfollowed by a head movement by the user. This mode mimics the experienceof sitting in the front row of a movie theater where to view the wideangle movie image, the viewer cannot comfortably view the whole moviescreen with eye movement alone and instead must move their eyes alongwith their head to see the peripheral areas of the movie screen. Toenable this mode, the head worn display requires apparatus for detectingeye movements that are associated with the optics assembly 16900, alongwith an inertial measurement unit to detect head movement. As such, themode detects the desire of the user to view a peripheral portion of thedisplayed image with the portion of the eye's field of view that hashigher acuity, by detecting a movement of the eye followed by a movementof the head in the same direction.

The displayed image is then moved laterally across the display field ofview in a direction that is opposite to the detected movements of theeye and head, wherein the magnitude and speed of the lateral movementcorrespond to the magnitude and speed of the detected movements of theeye and head. This lateral movement of the displayed image within thedisplay field of view provides the user with an improved view of theperipheral portion of the displayed image by moving the peripheralportion of the displayed image into the central sharp zone of thedisplay field of view and moving the peripheral portion of the displayedimage into a position where the user's eye is relatively centered. Inaddition, the lateral movement of the displayed image within the displayfield of view can be limited to that needed to center the edge of thedisplayed image within the display field of view. This mode addressesthe fact that it is uncomfortable for a user to move their eyes beyondan angle of approximately 15 to 20 degrees relative to their head formore than a short period of time and since head mounted displays areattached to the user's head, eye movement is the only way to visuallylook at different portions of the display field of view. This makes itdifficult for a user of a head worn display to comfortably view an imagethat has a visual size of larger than a 30 to 40 degrees included angle.The disclosed mode overcomes this limitation, by detecting when the userwould like to view a peripheral portion of a displayed image and thenlaterally moving the displayed image within the display field of view toa position where the peripheral portion of the displayed image can bemore comfortably viewed and where the peripheral portion of thedisplayed image is displayed with improved sharpness and highercontrast.

By triggering the lateral movement of the displayed image within thedisplay field of view based on the detection of a combined eye movementin a direction followed by a head movement in the same direction, themode is different from a world locked or body locked presentation of thedisplayed image in which lateral movement of the image occurs incorrespondence to head movement regardless of eye movement. Adescription of body locking of virtual objects in a head worn display isprovided for example in US Patent Publication 2014204759. Inembodiments, the lateral movement of the displayed image is limitedwithin the display field of view to that required to position the edgeof the displayed image in the center of the display field of view orsome other comfortable point within the field of view. Another examplewherein lateral movement of the image would not be wanted is when theuser only momentarily looks towards an edge or corner (e.g. a warninglight is blinking in the corner of the image and the user simply movestheir eye momentarily to verify the blinking light). In this case, theuser does not move their head and as a result lateral movement of theimage is not triggered and the displayed image remains stationary withinthe display field of view.

After an eye movement above a predetermined threshold has been detectedfollowed by a head movement in the same direction, the displayed imageis laterally moved (note that the method can also be used in acorresponding way for transverse or radial movements of the displayedimage within the display field of view) across the display field of viewin correspondence to and in an opposite direction to the detectedangular movement of the user's head. Eye movements can be detected forexample with an eye camera (e.g. as disclosed herein elsewhere) thatcaptures images of the user's eye while viewing the displayed image orby detecting changes in electric fields associated with the eye. Angularmovements of the user's head can be detected relative to the world,relative to the user's body through a motion sensor (e.g. IMU), etc.Fixing the displayed image in relation to the environment is good forviewing a wide angle image when the user is sitting or standing still.Fixing the displayed image in relation to the user's body is good forviewing a wide angle image when the user is walking, running or ridingin a vehicle. Angular movements of the user's head relative to theenvironment can be measured by, for example, either an inertialmeasurement unit in the head worn display or by image tracking ofobjects in the environment with a camera in the head worn display.Angular movement of the user's head relative to the user's body can bemeasured by a downward facing camera that can for example, captureimages of a portion of the user's body. The images of the portion of theuser's body are then analyzed to detect relative changes that can beused to detect movements of the user's head relative to the user's body.Alternatively, two inertial measurement units can be used to detectmovements of the user's head relative to the user's body, wherein one isattached to the head worn display and one is attached to the user's bodyand differential measurements are used to determine movements of theuser's head relative to the user's body. After an eye movement above thethreshold has been detected and a movement of the user head above athreshold has been detected as following the eye movement, lateralmovement of the displayed image across the display field of view isbegun. The speed of the lateral movement of the displayed image is incorrespondence to and in an opposite direction to the ensuing detectedhead movement. The lateral movement of the displayed image continuesuntil either the edge of the displayed image reaches the center of thedisplay field of view or the eye is detected to be looking at the centerof the display field of view (or within a predetermined threshold of thecenter of the display field of view) thereby indicating that theperipheral portion of the image that the user wanted to look at has beenreached.

FIGS. 180 and 181 are illustrations that show how the image is shiftedwithin the display field of view as the user moves their head. Note thatthe user's head is shown to the side of the image, because the image isactually presented to the user inside the head worn display. FIG. 180shows an image 18055 centered within the display field of view and theuser's head pointed straight ahead 18050. FIG. 181 shows the user's headpointed to the side 18150 and as a result, the image 18155 is shiftedwithin the display field of view in a direction that is opposed to themovement of the user's head, thereby leaving a blank portion 18130 wherethere is now no image content to display. In FIG. 182, the blank portionof the display field of view 18230 where the image has been shifted awayfrom is displayed as a dark region to enable the user to see-through tothe surrounding environment in the blank portion. However, in differentuse cases it may be advantageous to display the blank portion as aneutral gray or a color.

In embodiments, the user of a wide field of view head mounted display isprovided with an option to select the size (e.g. angular size) ofdisplayed images associated with different images or applications. Thedisplayed image is then resized to provide the selected angular imagesize for display to the user. For instance in a movie viewing mode, theuser may choose the displayed image to be approximately 30 degrees insize which mimics the experience of sitting in the back row of a movietheater where it is comfortable for the user to view the entiredisplayed image with eye movements alone. Alternately, the user maychoose the displayed image to be 50 degrees in size which mimics theexperience of sitting in the front row of a movie theater where thedisplayed image needs to be viewed with a combination of eye movementsand head movements with image shifting as previously described herein tocomfortably view the entire displayed image. FIG. 183 shows anillustration of a wide display field of view 18360, wherein a user canchoose to display a smaller field of view 18365 for a given image orapplication (e.g. a game) to improve the personal viewing experience.Where the smaller field of view 18365 enables the user to view the imageor application without having to move their eyes as much to see theentire image.

In embodiments, the display format is selected to have a narrow verticalfield of view relative to the horizontal field of view to enable thethickness of the optics to be reduced as measured across the loweroptics. Due to the angled orientation of the angled beam splitter 16950in the lower optics, the vertical field of view in the displayed imageis directly proportional to the thickness of the optics assembly. For agiven display field of view as measured along the diagonal of thedisplay field of view, reducing the vertical field of view and therebyincreasing the format ratio of the displayed image enables the thicknessof the optics assembly to be reduced. For example, for a 16:9 formatimage with a 50 degree diagonal field of view the thickness 18410 of theoptical assembly 18415 can be approximately 17 mm as shownillustratively in FIG. 184. If the format of the displayed image isincreased to 30:9 with a 50 degree diagonal field of view, the thickness18510 of the optical assembly 18515 can be approximately 10 mm as shownillustratively in FIG. 185. This represents approximately a 40%reduction in thickness of the optical assembly provided by changing to ahigher format ratio. FIG. 186 shows a 30:9 format field of view 18620and a 22:9 format field of view 18625, wherein the two fields of viewhave the same vertical field of view and different horizontal field ofview. By using a higher format ratio, a wide field of view can bedisplayed for use with augmented reality imagery in a relatively thinhead mounted display to improve the form factor of the head mounteddisplay. The high format ratio can be obtained by using a high formatratio emissive display or by using a normal format ratio emissivedisplay (e.g. 4:3, 16:9 or 22:9) and then using portions of the upperand lower regions of the emissive display. For example, the head mounteddisplay can include a 1080p emissive display which has 1920×1080 pixelsand a 30:9 image can be displayed by using 1920×576 pixels on theemissive display. A thin optics assembly would then be provided whichwas only capable of displaying an image comprised of the 576 pixels inthe vertical direction, but the optics can display an image comprised ofup to 1920 pixels horizontally. In the event that an image with adifferent format is to be displayed, it would be resized to fit theavailable display space (e.g. a 16:9 format image could be displayed asa 1024×576 pixel image and a 22:9 image can be displayed as a 1408×576pixel image or any other ratio associated with the number of pixelsavailable horizontally or vertically and the format of the image beingdisplayed). In a preferred embodiment, the display field of view has aformat ratio that is greater than 22:9. By having, for example, a formatratio such as 30:9, the center portion can be used for displaying 22:9image such as a movie, while the areas 13627 outside the 22:9 displayfield of view can be used for displaying auxiliary information thatdoesn't need to be as easily viewable or be presented with highresolution such as battery life, time, temperature, directional heading,whether new emails or texts are available.

In another embodiment, the central sharp zone of the display can be usedto display different types of images than the outer peripheral zone. Forexample, the central sharp zone can be used to display 22:9 or 16:9movie images that are resized to fit the number of pixels contained inthe central sharp zone. The outer peripheral zone can then be used likea second display where other types of information are displayed that canbe viewed at a lower resolution for a short period of time so that theuncomfortable eye position required is acceptable.

In yet another embodiment, the information displayed in the outerperipheral zone is rendered differently compared to the central sharpzone. This can include using larger font letters, higher contrastsettings or different colors to make the information presented in theouter peripheral zone more easily viewable.

In a further embodiment, the displayed image is adjusted incorrespondence to changes in the focus distance. To enable a measurementof the focus distance, a sensor may be provided to measure the distancebetween optical elements that are used to change the focus distance suchas between the image source 16910 and the lens elements 16920 or betweenthe lens elements 16920 and the lower optics. Wherein the displayedimage can be digitally adjusted to be larger or smaller to compensatefor magnification that may occur if the light rays between opticalelements is not telecentric. The displayed image can also be digitallyadjusted for distortion that may occur as the optical elements are movedto change the distance between the optical elements in accomplishing achange in focus distance. Where the change in focus distance may beassociated with an augmented reality operating mode such as a mode wherethe focus distance needs to be at a specific distance such as forexample at arm's length to allow the user to interact with displayedaugmented reality objects.

In a yet further embodiment, the optical assembly is designed to providetelecentric light to an optical surface that includes a triple notchmirror treatment to reduce the angular extent of the incident light andthereby improve the performance of the triple notch mirror. Where thetelecentric light can be incident onto the angled beam splitter or ontothe curved partial mirror. This embodiment can be particularly importantwhen the head worn display provides a wide field of view because triplenotch mirror are designed to be used at a specific angle with a limitedangular distribution around the specific angle. By providing telecentriclight to the triple notch mirror, the color uniformity and brightnessuniformity can be improved. In a further improvement, the wide angledisplayed image can be rendered to compensate for radially based colorand brightness rolloff by radially increasing the digital brightness(e.g. radially increase the code values and associated luma in theimage) and radially changing the color balance (e.g. color rendering) inthe image. In this way, the user is provided with an image that isperceived to have uniform brightness and uniform color in spite ofangular limitations of the triple notch mirror treatment affecting thedisplayed image over the wide display field of view.

Another aspect of the present invention relates to including a displaypanel in the head-worn computer that has an ability to present an imagethat is wider than needed for a use scenario such that the edges of thepanel can be left blank to allow for a shift in the displayed content.The displayed content can then be fully presented even when shiftedbecause the content can be shifted into the normally blank areas of thepanel. For example, a panel may be selected such that it can produce aSO degree field of view but the digital content may only consume 45degree field of view such that the whole content can still be viewed ifit is shifted by 2.5 degrees in either direction. As illustrated hereinelsewhere, in a wide field of view head-worn display system, the contentmay need to be shifted if the user is trying to look towards a far edgeof the content. In such situations, the system may begin with a reservedblank area on the edge(s) of the field of view to allow for a wholecontent shift. In other embodiments, the shifting into the reservededge(s) may be used when compensating the content for focal plane,convergence, etc.

In embodiments, the content presented in the field of view is of acontent type that is intended to take up all of the field of view, suchas when watching a movie. When the movie is presented, it is intended totake up as much of the field of view as can comfortably be viewed. Inembodiments, it is this type of full display content that is presentedwithin a middle section of the field of view with edges that are leftintentionally blank. This arrangement allows for the full displaycontent to be shifted into the unused edges to make the accommodationsillustrated herein.

In embodiments, the wide field of view display is used to enable thedisplayed image to be shifted laterally through digital shifting of theimage on the image source 110 to change the convergence distanceassociated with viewing of stereo images and thereby change theperceived distance to the displayed image. Where the convergencedistance can be changed in correspondence with the type of image beingdisplayed, the type of use case associated with augmented realityobjects being displayed or in response to detected characteristics ofthe user's eyes (e.g. such as can be detected with eye cameras) in thehead-worn display such as convergence distance or focus distance of theuser's eyes. FIG. 187 shows an illustration of the user's eyes 18721looking through display fields of view 18723. In this case, the user'seyes 18721 have parallel lines of sight 18725 so that the convergencepoint associated with the stereo images is approximately at infinity.The center portion of each display field of view 18723 is then used todisplay an image (shown as a dark area in the display fields of view18723) that does not occupy the entire display field of view 18723. Inthis way, the user perceives the stereo image comprised of the left andright images overlapped on top of each other to be presented atapproximately infinity from the convergence cue associated with theconvergence distance. Preferably, the focus distance is the same as theconvergence distance so that the focus cue associated with the focusdistance is the same as the convergence cue and the user thereby ispresented with a stereo image that has consistent stereo cues for a morecomfortable viewing experience. Importantly, in FIG. 187, there areportions of each display field of view 18723 that are unused to thesides of the displayed image because the displayed image does not occupythe entire horizontal angular extent of the display field of view 18723.Consequently, it is possible to shift the left and right imageslaterally within the display fields of view 18723 as shown in FIG. 188to provide a nearer convergence distance. Where the user's eyes 18821are shown in a slightly rotated position so that the lines of sight18825 are angled toward one another when looking through the centers ofthe left and right displayed images. This geometry is created byshifting the left and right displayed images toward each other withintheir respective display field of view 18823. FIG. 189 shows anillustration of the left and right displayed images (18911 and 18910) asthey would be presented within the display fields of view 18723 for thecase when the convergence distance is approximately infinity. FIG. 190shows an illustration of the left and right displayed images (19012 and19014) as they would be presented within the display fields of view18823 for the case when the convergence distance is nearer. Thus,providing a wide display field of view 18723 and 18823 with a narrowvertical field of view provides the additional benefit of convergencedistance adjustment by digitally shifting of the displayed image withinthe display field of view. Convergence distance adjustments can be usedto provide augmented reality images that are perceived to be atdifferent distances as required for certain application or desiredviewing experiences. This feature is particularly useful when thedisplayed image has a lower format ratio than the display field of view(e.g. the displayed image has a 22:9 format and the display field ofview has a 30:9 format) so that portions of the display field of vieware unused when displaying the left and right images. In an example,16:9 format stereo images are displayed in optics that provide 25:9format display fields of view wherein the stereo images are displayedwithout cropping so that the vertical angular extent of the displayedstereo images matches the vertical angular extent of the display fieldof view of the optics. To change the convergence distance from 8 feet to2 feet requires the left and right displayed images to be digitallyshifted towards each other by approximately 10% of the horizontalangular extent of each of the displayed images (e.g. for a 1280×720pixel image, the digital shift amounts to 146 pixels). This examplechange of convergence distance is well suited to changing betweenimaging use cases such as for changing from watching a movie with theimage perceived to be at 8 feet, to interacting with an augmentedreality object that requires the image to be perceived to be withinarm's reach by the user.

In yet another embodiment, the wide field of view display is used toenable the displayed image to be shifted laterally through digitalshifting of the image on the image source 110 to change theinterpupillary distance between the displayed images. FIG. 191 shows anillustration of the user's eyes 19121 looking through display fields ofview 19123 wherein the user's eyes 19121 have a larger interpupillarydistance between them than the user's eyes 18721 shown in FIG. 187. Inboth FIGS. 187 and 191, the user's eyes 18721 and 19121 have parallellines of sight 18725 and 19125 respectively so that the convergencepoint associated with the stereo images is approximately at infinity.The center portions of each display field of view 18723 and 19123 areused to display images (shown as dark areas within the display fields ofview 18723 and 19123) that do not occupy the entire display fields ofview 18723 and 19123. However, since the user's eyes 19121 in this casehave a wider interpupillary distance, the left and right images arelaterally shifted within the display fields of view 19123 by digitallyshifting the image on the image source 110 as shown in FIG. 191 toposition the images further apart as seen by the user within the displayfields of view 19123 and to thereby provide the lines of sight 19125 asdesired. Where the user's eyes 19121 are shown in a parallel position sothat the lines of sight 19125 are parallel when looking through thecenters of the left and right displayed images. This geometry is createdby shifting the left and right displayed images apart from each otherwithin their respective display fields of view 19123. FIG. 192 shows anillustration of the left and right displayed images (19212 and 19214) asthey would be presented within the display fields of view 19123 or asseen on the image source 110, for the case when the convergence distanceis approximately infinity and the user's eyes 19121 have a largeinterpupillary distance. Again, providing a wide horizontal displayfield of view 19123 with a narrow vertical field of view provides theadditional benefit of a digital method of adjusting for interpupillarydistance by digitally shifting of the displayed image within the displayfield of view.

In a preferred embodiment, the portions of the display field of viewthat are used for lateral shifting of the image amount to 10% or greaterof the display field of view. As such, while these portions of thedisplay field of view are unused for displaying an image, they are usedfor positioning the image for the purpose of providing a desiredconvergence distance or adjusting the interpupillary distance of thedisplayed left and right images. As can be seen in FIGS. 189, 190 and192, as the displayed image is laterally shifted within the displayfield of view by digitally shifting the image on the image source, theblank or unused portions of the display field of view, change in theirrelative size to the left and right of the displayed image whilemaintaining a constant total amount. In a further preferred embodiment,the total amount of the blank or unused portions of the display field ofview amount to 10% or greater of the display field of view.

Although embodiments of HWC have been described in language specific tofeatures, systems, computer processes and/or methods, the appendedclaims are not necessarily limited to the specific features, systems,computer processes and/or methods described. Rather, the specificfeatures, systems, computer processes and/or and methods are disclosedas non-limited example implementations of HWC.

All documents referenced herein are hereby incorporated by reference.

1. A wearable head device comprising: an illumination source configuredfor illuminating an eye of a user of the wearable head device, the eyehaving an iris, wherein illuminating the eye produces an eye glint; aone or more sensors configured to capture an image of the eye glint andfurther to capture an image of the iris; and one or more processorsconfigured to perform a method comprising: comparing, based on the imageof the eye glint and further based on the image of the iris, a positionof the iris with a position of the eye glint; and determining, based onthe comparing, a view target of the user.
 2. The wearable head device ofclaim 1, further comprising a see-through display, wherein the viewtarget comprises a location in a surrounding environment visible to theuser via the see-through display.
 3. The wearable head device of claim1, further comprising a see-through display, wherein the view targetcomprises a location of a digital image visible to the user via thesee-through display.
 4. The wearable head device of claim 1, wherein theone or more sensors are further configured to capture an eye imagecomprising the image of the eye glint and the image of the iris.
 5. Thewearable head device of claim 4, wherein the eye glint and the iris donot overlap within the eye image.
 6. The wearable head device of claim1, wherein: the illumination source comprises an infrared illuminationsource; the one or more sensors comprises an infrared camera; thewearable head device further comprises a filter configured to transmitvisible light and to absorb infrared light; and the filter is configuredto rest behind the illumination source with respect to the user.
 7. Thewearable head device of claim 1, wherein the one or more processors arefurther configured to execute an application, and the method furthercomprises presenting the view target as input to the application.
 8. Amethod comprising: illuminating, via an illumination source, an eye of auser of a wearable head device, the eye having an iris, whereinilluminating the eye produces an eye glint; capturing, via one or moresensors of the wearable head device, an image of the eye glint;capturing, via the one or more sensors, an image of the iris; comparing,based on the image of the eye glint and further based on the image ofthe iris, a position of the iris with a position of the eye glint; anddetermining, based on the comparing, a view target of the user.
 9. Themethod of claim 8, wherein: the wearable head device comprises asee-through display, and the view target comprises a location in asurrounding environment visible to the user via the see-through display.10. The method of claim 8, wherein: the wearable head device comprises asee-through display, and the view target comprises a location of adigital image visible to the user via the see-through display.
 11. Themethod of claim 8, further comprising capturing, via the one or moresensors, an eye image comprising the image of the eye glint and theimage of the iris.
 12. The method of claim 11, wherein the eye glint andthe iris do not overlap within the eye image.
 13. The method of claim 8,wherein: the illumination source comprises an infrared illuminationsource; the one or more sensors comprises an infrared camera; thewearable head device further comprises a filter configured to transmitvisible light and to absorb infrared light; and the filter is configuredto rest behind the illumination source with respect to the user.
 14. Themethod of claim 8, further comprising: executing an application via oneor more processors, and presenting the view target as input to theapplication.
 15. A non-transitory computer-readable storage mediumstoring instructions which, when executed by one or more processors,cause the one or more processors to perform a method comprising:illuminating, via an illumination source, an eye of a user of a wearablehead device, the eye having an iris, wherein illuminating the eyeproduces an eye glint; capturing, via one or more sensors of thewearable head device, an image of the eye glint; capturing, via the oneor more sensors, an image of the iris; comparing, based on the image ofthe eye glint and further based on the image of the iris, a position ofthe iris with a position of the eye glint; and determining, based on thecomparing, a view target of the user.
 16. The non-transitorycomputer-readable storage medium of claim 15, wherein: the wearable headdevice comprises a see-through display, and the view target comprises alocation in a surrounding environment visible to the user via thesee-through display.
 17. The non-transitory computer-readable storagemedium of claim 15, wherein: the wearable head device comprises asee-through display, and the view target comprises a location of adigital image visible to the user via the see-through display.
 18. Thenon-transitory computer-readable storage medium of claim 15, the methodfurther comprising capturing, via the one or more sensors, an eye imagecomprising the image of the eye glint and the image of the iris.
 19. Thenon-transitory computer-readable storage medium of claim 18, wherein theeye glint and the iris do not overlap within the eye image.
 20. Thenon-transitory computer-readable storage medium of claim 15, wherein:the illumination source comprises an infrared illumination source; theone or more sensors comprises an infrared camera; the wearable headdevice further comprises a filter configured to transmit visible lightand to absorb infrared light; and the filter is configured to restbehind the illumination source with respect to the user.